Hey guys, Im sorry to bothered you but Im kinda desperate and really need your help.
Im preparing for math exam and Ive got a 3 various problem
I know the right answers but Im not able to find out the method. I would really appreciate your help.
1. if cos x = -2/5 than cos 2x = ?? (i know it is -17/25)
or sin x = 3/5 and cos2x= ?? (7/25) but I have no clue how to do it.
2. the number of X (X is from (pi, 2pi) which is valid for sin^2x-sinx=0
(it is 0)
or X is from (0, 2pi) for sin^3x+sinx=0
(it is 1)
3. the last one
the imaginary part of the number
(-1 -i)^8 is (0)
or (1+i)^8 is (16)
(-2 -2i)^8 is (2^12)
(1+i)^32 is (0)
Much appreciate your help and time!