Question

f(x)=4sinx/1+cosx

find f'(x)

this is what i got and i dunno what i did to get it wrong

(4cos(x)+ 4cosx^2-4sin(x)^2)/cosx62

Answer 1

looks like a ± error, and your denominator is wrong

my first line of the derivative was

(1+cosx)(4cosx) - 4sinx(-sinx))/(1+cosx)^2 using the quotient rule
expanding :
(4cosx + 4cos^2x + 4sin^2x)/(1+cosx)^2
= 4(cosx + 1)/(1+cosx)^2 , remember sin^2x+cos^2 = 1
= 4/(1+cosx)