Which value for x is a solution to cosx = sqrt of 2/2?

a) -9pi/4
b) 3pi/4
c) -3pi/4
d) 4pi/3

What is the first step I should do?

1 answer

45 degrees in quadrant 1 or 4
45 degrees = pi/4

-9 (pi/4) is -pi/4 which is 45 degrees in Q 4