Question

( begin{aligned}left|begin{array}{ccc}cos x & 1 & 0 1 & 2 cos x & 1 0 & 1 & 2 cos xend{array}right|=-1(2 cos x-0) &=4 cos ^{3} x-10 x-2 cos x &=4 cos ^{3} x-3 cos x & int_{0}^{pi / 2} F(x) d x=int_{0}^{pi / 2} cos x=frac{1}{3}|sin 3 x|_{0}^{x / 2}=-frac{1}{3} end{aligned} )

# cos x 1 12. Iff(x) = 1 2cosx 0 1 70/2 0 1 , then [f(x) dx = 2 cos x

Solution