#1**+1 **

Sin(θ)=cos (θ)

Tan (θ)=cot (θ)

sine and **co**sine

tangent and **co**tenagent.

see that **co**?

That stands for **co**mplimentary .. and

Complimentary angles add to 90 degrees

so

\(Sin(\theta)=cosine (90-\theta)\\ so\;\;if\\ Sin(\theta)=cosine (\theta)\;\;then\\ \theta = 90-\theta\\ 2\theta=90\\ \theta=45^\circ\\ \text{of course there are an infinite number of answers but they are all of the from}\\ \theta =45+2\pi n\qquad n\in Z \)

You can do the other one yourself :)

Melody Jul 1, 2017