Is this answer a mistake?



MA005 section 3.5 Practice Problems number 37.
The question is: Find the derivative of: d/dz sqrt(1+(cosz)^2)
The answer given is: (-sin(2z))/(2 sqrt(1+(cosz)^2)
Shouldn’t the answer be: -coszsinz/(sqrt(1+(cosz)^2)?
If no, then why not?
link to the question page:
link to the answer page:


I think your answer is correct, but so is the given answer. There was a bit more simplification in the given answer where the trig double angle formula was used. In your case, -cos(z)sin(z)=sin(2*z)/2.

Math answers often appear in different but equivalent forms .

Good Luck!