来自彭晓的问题
已知sin(π-α)-cos(π+α)=根号2/3求下列各式的值(1)sinα-cosα(2)sin^2(π/2-α)-cos^2(π/2+α)
已知sin(π-α)-cos(π+α)=根号2/3求下列各式的值
(1)sinα-cosα
(2)sin^2(π/2-α)-cos^2(π/2+α)
1回答
2020-02-06 10:31
已知sin(π-α)-cos(π+α)=根号2/3求下列各式的值(1)sinα-cosα(2)sin^2(π/2-α)-cos^2(π/2+α)
已知sin(π-α)-cos(π+α)=根号2/3求下列各式的值
(1)sinα-cosα
(2)sin^2(π/2-α)-cos^2(π/2+α)
(1)由题得:sinα+cosα=根号2/3所以,(sinα+cosα)²=2/9所以,sin²α+2sinα*cosα+cos²α=2/9因为,sin²α+cos²α=1所以,sinα*cosα=-7/18又因为,(sinα-cosα)²=(sinα+cosα)&s...