I have done another one, which is f(x)= 8arcsin(x^4);

f’(x) = 8 (1/(sqrt(1 – (x^4)^2))*4x^3 =>

f’(x)=32x^3/(sqrt(1 – (x^4)^2))=>

f’(x)=32x^3/(sqrt(1 – (x^8))=>, after that

f’(0.8) = 32*0.512/(sqrt(1 – 0.16777216) =>

f’(0.8) = 16, 384/ (sqrt 0.83222784) = 16, 384/ (0.91226) = 17, 95979

Didn't apply the logs this time (but I wanted so much )

Thanks