What formula gives the x coordinate of the maximum value for y=cos(x)

Hints:
cos(x) has a maximum at x=0.
It is also a periodic function with a period of 2pi.

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.