# Thread: using cofunction identities

1. ## using cofunction identities

1. cos^2(44°) + cos^2(46°)

2. sin2 (79°) + sin2 (53°) + sin2 (37°) + sin2 (11°)

3. Solve the equation for x. Use n as an integer constant.

thanks!

2. Originally Posted by mashley
1. cos^2(44°) + cos^2(46°)

2. sin2 (79°) + sin2 (53°) + sin2 (37°) + sin2 (11°)

3. Solve the equation for x. Use n as an integer constant.

thanks!
On #1. Note that $\displaystyle \cos (44^0)=\cos (90^0-46^0)$
then use the formula $\displaystyle \cos (x-y)=\cos x\cos y + \sin x\sin y$ to simply your answer.

On #2. A similar strategy can be used like #1. Rewrite some of the angles into sums or differences and simply.

On #3. When you get down to $\displaystyle sin(x)=\frac{-1}{\sqrt{2}}$, think about what angles give you such value. It is going to be something "special".

3. Originally Posted by chabmgph
On #3. When you get down to $\displaystyle sin(x)=\frac{-1}{\sqrt{2}}$, think about what angles give you such value. It is going to be something "special".
I have the same problems as the original poster. I can't seem to get #3 though.

Help?

Edit: Nevermind, got it.