Polar Coordinates and Polar Graphs

Hello, I am having a dificult time working these problesms. I made an attempt to work them out unfortunately my book does not show the answers. So I have no clue if I am following the right steps. Could anyone please correct my answers if they are wrong and please explain in details how you found the answers? Thank you!

1) Plot the points in polar coordinates and find the corresponding rectangular coordinates for the points.

a) (-2, 7pi/4 ) answer: (-1.41, -1.41)

b) (0, -7pi/6 ) answer: ( 0, 0)

c) (-3, -1.57 ) answer: ( 3.39, 0.42)

2) The rectangular coordinates are given. Find two sets of polar coordinates for the given points for

0 is less than or equal to Theta which is less than 2 pi.

a) (0, -5) answer: (5, -pi/4) ; (-5, -5pi/4)

b) (4, -2) answer: (4.47, -26.56 degrees) ; (-4.47, 180 degrees)

c) (3, (-3)^1/2 ) answer: ( 3.46, -pi/ 6) ; -3.46, 7pi/6)

( I change my radicals in decimals I hope you don't mind. It makes it easier to type)