求y=sin²x-sinxcosx+2(x∈﹙-π/4,π/4﹚的值域
问题描述:
求y=sin²x-sinxcosx+2(x∈﹙-π/4,π/4﹚的值域
答
y=sin²x-sinxcosx+2=(1-cos2x)/2-sin(2x)/2+2=-√ 2/2 *sin(2x+π/4)+5/2∵x∈﹙-π/4,π/4),∴(2x∈(-π/2,π/2)∴(2x+π/4)∈(-π/4,3π/4)∴sin(2x+π/4))∈(-√ 2/2,1)∴Y=-√ 2/2 *sin(2x+...