Question

一道数学题，急需，在线等

2乘以（sinα）的平方-4sinαcosα+20乘以(cosα)的 平方

Answer 1

2*[(sinα)^2]-4sinαcosα+20*[(cosα)^2]
=1-cos(2α)-2sin(2α)+20*[cos(2α)+1]/2
=1-cos(2α)-2sin(2α)+10cos(2α)+10
=11+9cos(2α)-2sin(2α)

Answer 2

三角函数公式的变形

Answer 3

9