Let f (x) = vector a · B, where vector a = (2, cos2x) and B = (1, - 2) find the monotone interval of F (x). When x belongs to [0, π / 3], find the range of F (x). To ensure the accuracy of the method, the following formula is used

Let f (x) = vector a · B, where vector a = (2, cos2x) and B = (1, - 2) find the monotone interval of F (x). When x belongs to [0, π / 3], find the range of F (x). To ensure the accuracy of the method, the following formula is used

a=(2,cos2x),b=(1,-2)
So f (x) = a * b = 2-2cos2x
Monotone increasing interval:
2kπ