已知sinx=根号5/5,则sin^4x-cos^4x的值()
问题描述:
已知sinx=根号5/5,则sin^4x-cos^4x的值()
答
sin^4x-cos^4x
=(sin²x+cos²x)(sin²x-cos²x)
=sin²x-cos²x
=2sin²x-1
=2×(√5/5)²-1
=2/5-1
=-3/5