Question

Tell me what i'm doing wrong, picture is attached.

Answer 1

3rd to 4th line - the numerator shows s^3 but a c appeared

Answer 2

You also made a mistake on the RHS. You can't cross out the sin's and cos's like that.

Answer 3

Instead there is a trig identity there.

Answer 4

how do i fix this ? :S

Answer 5

There is a trig identity on the RHS.

Answer 6

At the 4th line, try combining the denominator