# Thread: Trig Expressions problem

1. ## Trig Expressions problem

Hello, this is my first post here as I have been lurking here for quiet a while but I have just now registered. I have a quick trig question.

How would I do this?

cotθcosθ

I got up to here, but then I don't know what to do:

( cosθ / sinθ ) ( cosθ) = ( cos^2θ / sinθ )

Thanks.

2. Originally Posted by Intrusion
Hello, this is my first post here as I have been lurking here for quiet a while but I have just now registered. I have a quick trig question.

How would I do this?

cotθcosθ

I got up to here, but then I don't know what to do:

( cosθ / sinθ ) ( cosθ) = ( cos^2θ / sinθ )

Thanks.
There seems to be something missing from this. What are we supposed to do with $\cot\left(\vartheta\right)\cos\left(\vartheta\righ t)$??

3. Oops! Sorry I forgot to mention that it says to write each expression in terms of sine or cosine only.

4. Originally Posted by Intrusion
Oops! Sorry I forgot to mention that it says to write each expression in terms of sine or cosine only.
In that case then...

You're work is good. To get it in terms of sine, just apply the identity $\cos^2\left(\vartheta\right)=1-\sin^2\left(\vartheta\right)$.

5. How do I do that? :/

6. Identity: $\color{red} \cos^2 \theta = 1 - \sin^2 \theta$

What you have: $\frac{\color{red}\cos^2 \theta}{\sin \theta}$

How do I do that? :/
I dunno.

7. Oh, LOL! Thanks. xD