Confused about cosec(x).
$begingroup$
The title says it all, let's take this simple example:
I want to find $c$.
Using sine I get:
$sin(30)$ = $4 / c$
- $c = 4 / sin(30) = 8$
Now, using $cosec$:
- $cosec(30) = c / 4$
- $c = cosec(30) * 4 = 8$
But also:
- $cosec(30) = c / 4$
- $tan(30) = 4 / a$
- $4 = tan(30) * a$
- $c = cosec(30)cdot tan(30)cdot c = ccdot (c / 4)cdot (4 / a) = c$
- OR: $cosec(30) cdot tan(30)cdot c = sec(30)cdot c approx c$
What's gone wrong here, I assumed $c$ would cancel out?
EDIT 1: Why isn't $c$ cancelling out in the last example, even after the fix?
EDIT 2: Fixed steps 2 and 3 (changed $c$ to $a$). Thank you for your help, silly mistakes.
geometry trigonometry
$endgroup$
add a comment |
$begingroup$
The title says it all, let's take this simple example:
I want to find $c$.
Using sine I get:
$sin(30)$ = $4 / c$
- $c = 4 / sin(30) = 8$
Now, using $cosec$:
- $cosec(30) = c / 4$
- $c = cosec(30) * 4 = 8$
But also:
- $cosec(30) = c / 4$
- $tan(30) = 4 / a$
- $4 = tan(30) * a$
- $c = cosec(30)cdot tan(30)cdot c = ccdot (c / 4)cdot (4 / a) = c$
- OR: $cosec(30) cdot tan(30)cdot c = sec(30)cdot c approx c$
What's gone wrong here, I assumed $c$ would cancel out?
EDIT 1: Why isn't $c$ cancelling out in the last example, even after the fix?
EDIT 2: Fixed steps 2 and 3 (changed $c$ to $a$). Thank you for your help, silly mistakes.
geometry trigonometry
$endgroup$
1
$begingroup$
Item $2$ is the error. $tan 30=frac4a$ is what it should be.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@MattSamuel thank you, been a long night :)!
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
My advice is too never use $sec$ or $operatorname{cosec}$. And if you are imposed to work with them, translate a soon as possible to $sin,cos$.
$endgroup$
– zwim
5 hours ago
$begingroup$
@zwim, thanks for the advice, I just got a bit OCD over this as it didn't add up (well still doesn't).
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
@zwim I think this advice is a bit extreme. While I see where you're coming from, they have a name for a reason. For instance, $1+tan^2 x=sec^2 x$.
$endgroup$
– Matt Samuel
4 hours ago
add a comment |
$begingroup$
The title says it all, let's take this simple example:
I want to find $c$.
Using sine I get:
$sin(30)$ = $4 / c$
- $c = 4 / sin(30) = 8$
Now, using $cosec$:
- $cosec(30) = c / 4$
- $c = cosec(30) * 4 = 8$
But also:
- $cosec(30) = c / 4$
- $tan(30) = 4 / a$
- $4 = tan(30) * a$
- $c = cosec(30)cdot tan(30)cdot c = ccdot (c / 4)cdot (4 / a) = c$
- OR: $cosec(30) cdot tan(30)cdot c = sec(30)cdot c approx c$
What's gone wrong here, I assumed $c$ would cancel out?
EDIT 1: Why isn't $c$ cancelling out in the last example, even after the fix?
EDIT 2: Fixed steps 2 and 3 (changed $c$ to $a$). Thank you for your help, silly mistakes.
geometry trigonometry
$endgroup$
The title says it all, let's take this simple example:
I want to find $c$.
Using sine I get:
$sin(30)$ = $4 / c$
- $c = 4 / sin(30) = 8$
Now, using $cosec$:
- $cosec(30) = c / 4$
- $c = cosec(30) * 4 = 8$
But also:
- $cosec(30) = c / 4$
- $tan(30) = 4 / a$
- $4 = tan(30) * a$
- $c = cosec(30)cdot tan(30)cdot c = ccdot (c / 4)cdot (4 / a) = c$
- OR: $cosec(30) cdot tan(30)cdot c = sec(30)cdot c approx c$
What's gone wrong here, I assumed $c$ would cancel out?
EDIT 1: Why isn't $c$ cancelling out in the last example, even after the fix?
EDIT 2: Fixed steps 2 and 3 (changed $c$ to $a$). Thank you for your help, silly mistakes.
geometry trigonometry
geometry trigonometry
edited 4 hours ago
Shibalicious
asked 5 hours ago
ShibaliciousShibalicious
1245
1245
1
$begingroup$
Item $2$ is the error. $tan 30=frac4a$ is what it should be.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@MattSamuel thank you, been a long night :)!
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
My advice is too never use $sec$ or $operatorname{cosec}$. And if you are imposed to work with them, translate a soon as possible to $sin,cos$.
$endgroup$
– zwim
5 hours ago
$begingroup$
@zwim, thanks for the advice, I just got a bit OCD over this as it didn't add up (well still doesn't).
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
@zwim I think this advice is a bit extreme. While I see where you're coming from, they have a name for a reason. For instance, $1+tan^2 x=sec^2 x$.
$endgroup$
– Matt Samuel
4 hours ago
add a comment |
1
$begingroup$
Item $2$ is the error. $tan 30=frac4a$ is what it should be.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@MattSamuel thank you, been a long night :)!
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
My advice is too never use $sec$ or $operatorname{cosec}$. And if you are imposed to work with them, translate a soon as possible to $sin,cos$.
$endgroup$
– zwim
5 hours ago
$begingroup$
@zwim, thanks for the advice, I just got a bit OCD over this as it didn't add up (well still doesn't).
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
@zwim I think this advice is a bit extreme. While I see where you're coming from, they have a name for a reason. For instance, $1+tan^2 x=sec^2 x$.
$endgroup$
– Matt Samuel
4 hours ago
1
1
$begingroup$
Item $2$ is the error. $tan 30=frac4a$ is what it should be.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
Item $2$ is the error. $tan 30=frac4a$ is what it should be.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@MattSamuel thank you, been a long night :)!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
@MattSamuel thank you, been a long night :)!
$endgroup$
– Shibalicious
5 hours ago
1
1
$begingroup$
My advice is too never use $sec$ or $operatorname{cosec}$. And if you are imposed to work with them, translate a soon as possible to $sin,cos$.
$endgroup$
– zwim
5 hours ago
$begingroup$
My advice is too never use $sec$ or $operatorname{cosec}$. And if you are imposed to work with them, translate a soon as possible to $sin,cos$.
$endgroup$
– zwim
5 hours ago
$begingroup$
@zwim, thanks for the advice, I just got a bit OCD over this as it didn't add up (well still doesn't).
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
@zwim, thanks for the advice, I just got a bit OCD over this as it didn't add up (well still doesn't).
$endgroup$
– Shibalicious
5 hours ago
1
1
$begingroup$
@zwim I think this advice is a bit extreme. While I see where you're coming from, they have a name for a reason. For instance, $1+tan^2 x=sec^2 x$.
$endgroup$
– Matt Samuel
4 hours ago
$begingroup$
@zwim I think this advice is a bit extreme. While I see where you're coming from, they have a name for a reason. For instance, $1+tan^2 x=sec^2 x$.
$endgroup$
– Matt Samuel
4 hours ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
$$tan(30°)=frac{4}{a}text{ which isn't } frac{4}{c}$$
Now we have that $$c=text{cosec}(30°)·4;text{ and } ;4=tan(30)°·a$$
Thus $$c=text{cosec}(30°)·tan(30°)·a=frac{c}{4}·frac{4}{a}·anot= frac{c}{4}·frac{4}{a}·color{red}{c}$$ as pointed out in the comments
$endgroup$
$begingroup$
Thank you for spotting this, got it!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
No problem! @Shibalicious
$endgroup$
– Dr. Mathva
5 hours ago
$begingroup$
So now I got sec(30) * c, which is c ~= 9.23, why?
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
I've edited the answer
$endgroup$
– Dr. Mathva
4 hours ago
1
$begingroup$
Spot on, I got it now!
$endgroup$
– Shibalicious
4 hours ago
|
show 2 more comments
$begingroup$
$$sec30^{circ}=frac{1}{cos30^{circ}}=frac{2}{sqrt3}.$$
$endgroup$
$begingroup$
This is a non sequitur.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Dr.Mathva It's just a post of an arbitrary fact. What does this have to do with the question?
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Matt Samuel I wrote where was a mistake. See please better. It's exactly, that you wrote.
$endgroup$
– Michael Rozenberg
5 hours ago
1
$begingroup$
The only place I see $sec 30$ is already well after the first error. It's true that it's an error thinking it's equal to $1$, but that's not the important error.
$endgroup$
– Matt Samuel
5 hours ago
add a comment |
Your Answer
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2 Answers
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oldest
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2 Answers
2
active
oldest
votes
active
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votes
$begingroup$
$$tan(30°)=frac{4}{a}text{ which isn't } frac{4}{c}$$
Now we have that $$c=text{cosec}(30°)·4;text{ and } ;4=tan(30)°·a$$
Thus $$c=text{cosec}(30°)·tan(30°)·a=frac{c}{4}·frac{4}{a}·anot= frac{c}{4}·frac{4}{a}·color{red}{c}$$ as pointed out in the comments
$endgroup$
$begingroup$
Thank you for spotting this, got it!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
No problem! @Shibalicious
$endgroup$
– Dr. Mathva
5 hours ago
$begingroup$
So now I got sec(30) * c, which is c ~= 9.23, why?
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
I've edited the answer
$endgroup$
– Dr. Mathva
4 hours ago
1
$begingroup$
Spot on, I got it now!
$endgroup$
– Shibalicious
4 hours ago
|
show 2 more comments
$begingroup$
$$tan(30°)=frac{4}{a}text{ which isn't } frac{4}{c}$$
Now we have that $$c=text{cosec}(30°)·4;text{ and } ;4=tan(30)°·a$$
Thus $$c=text{cosec}(30°)·tan(30°)·a=frac{c}{4}·frac{4}{a}·anot= frac{c}{4}·frac{4}{a}·color{red}{c}$$ as pointed out in the comments
$endgroup$
$begingroup$
Thank you for spotting this, got it!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
No problem! @Shibalicious
$endgroup$
– Dr. Mathva
5 hours ago
$begingroup$
So now I got sec(30) * c, which is c ~= 9.23, why?
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
I've edited the answer
$endgroup$
– Dr. Mathva
4 hours ago
1
$begingroup$
Spot on, I got it now!
$endgroup$
– Shibalicious
4 hours ago
|
show 2 more comments
$begingroup$
$$tan(30°)=frac{4}{a}text{ which isn't } frac{4}{c}$$
Now we have that $$c=text{cosec}(30°)·4;text{ and } ;4=tan(30)°·a$$
Thus $$c=text{cosec}(30°)·tan(30°)·a=frac{c}{4}·frac{4}{a}·anot= frac{c}{4}·frac{4}{a}·color{red}{c}$$ as pointed out in the comments
$endgroup$
$$tan(30°)=frac{4}{a}text{ which isn't } frac{4}{c}$$
Now we have that $$c=text{cosec}(30°)·4;text{ and } ;4=tan(30)°·a$$
Thus $$c=text{cosec}(30°)·tan(30°)·a=frac{c}{4}·frac{4}{a}·anot= frac{c}{4}·frac{4}{a}·color{red}{c}$$ as pointed out in the comments
edited 4 hours ago
answered 5 hours ago
Dr. MathvaDr. Mathva
1,975322
1,975322
$begingroup$
Thank you for spotting this, got it!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
No problem! @Shibalicious
$endgroup$
– Dr. Mathva
5 hours ago
$begingroup$
So now I got sec(30) * c, which is c ~= 9.23, why?
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
I've edited the answer
$endgroup$
– Dr. Mathva
4 hours ago
1
$begingroup$
Spot on, I got it now!
$endgroup$
– Shibalicious
4 hours ago
|
show 2 more comments
$begingroup$
Thank you for spotting this, got it!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
No problem! @Shibalicious
$endgroup$
– Dr. Mathva
5 hours ago
$begingroup$
So now I got sec(30) * c, which is c ~= 9.23, why?
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
I've edited the answer
$endgroup$
– Dr. Mathva
4 hours ago
1
$begingroup$
Spot on, I got it now!
$endgroup$
– Shibalicious
4 hours ago
$begingroup$
Thank you for spotting this, got it!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
Thank you for spotting this, got it!
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
No problem! @Shibalicious
$endgroup$
– Dr. Mathva
5 hours ago
$begingroup$
No problem! @Shibalicious
$endgroup$
– Dr. Mathva
5 hours ago
$begingroup$
So now I got sec(30) * c, which is c ~= 9.23, why?
$endgroup$
– Shibalicious
5 hours ago
$begingroup$
So now I got sec(30) * c, which is c ~= 9.23, why?
$endgroup$
– Shibalicious
5 hours ago
1
1
$begingroup$
I've edited the answer
$endgroup$
– Dr. Mathva
4 hours ago
$begingroup$
I've edited the answer
$endgroup$
– Dr. Mathva
4 hours ago
1
1
$begingroup$
Spot on, I got it now!
$endgroup$
– Shibalicious
4 hours ago
$begingroup$
Spot on, I got it now!
$endgroup$
– Shibalicious
4 hours ago
|
show 2 more comments
$begingroup$
$$sec30^{circ}=frac{1}{cos30^{circ}}=frac{2}{sqrt3}.$$
$endgroup$
$begingroup$
This is a non sequitur.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Dr.Mathva It's just a post of an arbitrary fact. What does this have to do with the question?
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Matt Samuel I wrote where was a mistake. See please better. It's exactly, that you wrote.
$endgroup$
– Michael Rozenberg
5 hours ago
1
$begingroup$
The only place I see $sec 30$ is already well after the first error. It's true that it's an error thinking it's equal to $1$, but that's not the important error.
$endgroup$
– Matt Samuel
5 hours ago
add a comment |
$begingroup$
$$sec30^{circ}=frac{1}{cos30^{circ}}=frac{2}{sqrt3}.$$
$endgroup$
$begingroup$
This is a non sequitur.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Dr.Mathva It's just a post of an arbitrary fact. What does this have to do with the question?
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Matt Samuel I wrote where was a mistake. See please better. It's exactly, that you wrote.
$endgroup$
– Michael Rozenberg
5 hours ago
1
$begingroup$
The only place I see $sec 30$ is already well after the first error. It's true that it's an error thinking it's equal to $1$, but that's not the important error.
$endgroup$
– Matt Samuel
5 hours ago
add a comment |
$begingroup$
$$sec30^{circ}=frac{1}{cos30^{circ}}=frac{2}{sqrt3}.$$
$endgroup$
$$sec30^{circ}=frac{1}{cos30^{circ}}=frac{2}{sqrt3}.$$
answered 5 hours ago
Michael RozenbergMichael Rozenberg
105k1892197
105k1892197
$begingroup$
This is a non sequitur.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Dr.Mathva It's just a post of an arbitrary fact. What does this have to do with the question?
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Matt Samuel I wrote where was a mistake. See please better. It's exactly, that you wrote.
$endgroup$
– Michael Rozenberg
5 hours ago
1
$begingroup$
The only place I see $sec 30$ is already well after the first error. It's true that it's an error thinking it's equal to $1$, but that's not the important error.
$endgroup$
– Matt Samuel
5 hours ago
add a comment |
$begingroup$
This is a non sequitur.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Dr.Mathva It's just a post of an arbitrary fact. What does this have to do with the question?
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Matt Samuel I wrote where was a mistake. See please better. It's exactly, that you wrote.
$endgroup$
– Michael Rozenberg
5 hours ago
1
$begingroup$
The only place I see $sec 30$ is already well after the first error. It's true that it's an error thinking it's equal to $1$, but that's not the important error.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
This is a non sequitur.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
This is a non sequitur.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Dr.Mathva It's just a post of an arbitrary fact. What does this have to do with the question?
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Dr.Mathva It's just a post of an arbitrary fact. What does this have to do with the question?
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@Matt Samuel I wrote where was a mistake. See please better. It's exactly, that you wrote.
$endgroup$
– Michael Rozenberg
5 hours ago
$begingroup$
@Matt Samuel I wrote where was a mistake. See please better. It's exactly, that you wrote.
$endgroup$
– Michael Rozenberg
5 hours ago
1
1
$begingroup$
The only place I see $sec 30$ is already well after the first error. It's true that it's an error thinking it's equal to $1$, but that's not the important error.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
The only place I see $sec 30$ is already well after the first error. It's true that it's an error thinking it's equal to $1$, but that's not the important error.
$endgroup$
– Matt Samuel
5 hours ago
add a comment |
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1
$begingroup$
Item $2$ is the error. $tan 30=frac4a$ is what it should be.
$endgroup$
– Matt Samuel
5 hours ago
$begingroup$
@MattSamuel thank you, been a long night :)!
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
My advice is too never use $sec$ or $operatorname{cosec}$. And if you are imposed to work with them, translate a soon as possible to $sin,cos$.
$endgroup$
– zwim
5 hours ago
$begingroup$
@zwim, thanks for the advice, I just got a bit OCD over this as it didn't add up (well still doesn't).
$endgroup$
– Shibalicious
5 hours ago
1
$begingroup$
@zwim I think this advice is a bit extreme. While I see where you're coming from, they have a name for a reason. For instance, $1+tan^2 x=sec^2 x$.
$endgroup$
– Matt Samuel
4 hours ago