求证sin²(α-30°)+cos²α+sin(α-30°)cosα=3/4

问题描述:

求证sin²(α-30°)+cos²α+sin(α-30°)cosα=3/4

=(3/4sina*sina+1/4cosa*cosa-根号3/2sina*cosa)+cosa*cosa+根号3/2sina*cosa-1/2cosa*cosa
=3/4sina*sina+3/4cosa*cosa
=3/4