I have no idea how to do these problems on my review, can someone please explain how to do these.

1. -2+5i= r(cosθ+isinθ), find θ accurate to 3 decimal places. Be sure your answer is in the correct quadrant.

2. If θis an angle in the third quadrant and sinθ= -1/5 find the exact value of tan2θ.I did not rationalize the denominator.r(cos

3. If 2+5i =θ+isinθ), find r.