# Trig Identities - solve the following for 0 <_ θ <_ 4pi

• Dec 27th 2012, 11:50 AM
dcpc10
Trig Identities - solve the following for 0 <_ θ <_ 4pi
solve the following for 0 <_ θ <_ 4pi

The <_ represents less than or equal to.

Sin[θ]^2 == -Cos[θ]

Would like a step by step process for approaching this question. Thanks.
• Dec 27th 2012, 11:58 AM
Plato
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
Quote:

Originally Posted by dcpc10
solve the following for 0 <_ θ <_ 4pi
Sin[θ]^2 == -Cos[θ]

If the question is to solve $\displaystyle \sin^2(\theta)=-\cos(\theta)$ then that is equivalent to solving $\displaystyle \cos^2(\theta)-\cos(\theta)-1=0$.

Or $\displaystyle u^2-u-1=0$ where $\displaystyle u=\cos(\theta).$

If that is not what it means, then please correct it.
• Dec 27th 2012, 12:10 PM
dcpc10
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
Yes that is what it means.
• Dec 27th 2012, 12:29 PM
HallsofIvy
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
So you can solve it now?
• Dec 27th 2012, 01:17 PM
dcpc10
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
No because I would appreciate a step by step process to solve it. That was the reasoning for making the thread in the first place. This is for gr 12 advanced functions.
• Dec 27th 2012, 01:23 PM
Plato
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
Quote:

Originally Posted by dcpc10
No because I would appreciate a step by step process to solve it. That was the reasoning for making the thread in the first place. This is for gr 12 advanced functions.

Show us your solution to $\displaystyle u^2-u-1=0$.
• Dec 27th 2012, 01:37 PM
dcpc10
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
• Dec 27th 2012, 01:41 PM
Plato
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
Quote:

Originally Posted by dcpc10

Go and learn to do middle school algebra.
We are not a tutorial service.
• Dec 27th 2012, 02:09 PM
dcpc10
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
Very unhelpful, you fail to communicate what requires solving and instead would rather confuse those seeking assistance. This is not a tutoring service obviously but its suppose to be a "math help" forum so it totally defeats the purpose if you are unwilling to help solve the problem at hand. Why would you ask me to solve a question totally unrelated if I do not know how it connects to the end answer? That is not going to help anyone. Geez very disappointing..
• Dec 28th 2012, 10:38 AM
kinhew93
Re: Trig Identities - solve the following for 0 <_ θ <_ 4pi
Do you know how to solve cos(θ) = k?
Do you know the identity sin^2(θ) + cos^2(θ) == 1?