How to find the Derivative

what is the derivative of

(x-2)-(sin2x/4)

2csc^3(sqrt(x))

I got -3cscxcotx/(sqrt(x))-which I know is wrong

cos^3(5x^2-6)

I got 30cos^2(5x^2-6)(-sin(5x^2-6)) --which I know is wrong too.

Thanks for the help

1/
y ' = 1 - (2/4)cos(2x) = 1 - (cos(2x))/2
2/
Chain rule
with u = sqrt(x)
---> y ' = -6csc^3x cotx (1/(2 sqrtx)) = ...simplify

3/
Chain rule
---> y ' = -30xcos^2(5x^2-6) sin(5x^2-6)

3) 30x cos^2(5x^2-6) sin(6-5x^2)
changing the sign of the argument of sin() absorbs the preceding minus sign

full step by step solution

http://symbolab.com/solutions/derivative…

good luck