不等式证明:已知a^2 + b^2 = 1 ,x^2 + y^2 = 1 ,求证ax + by ≤1
问题描述:
不等式证明:已知a^2 + b^2 = 1 ,x^2 + y^2 = 1 ,求证ax + by ≤1
答
设a=sinA,b=cosA x=sinB,y=cosB
则 ax+by=sinA*sinB+cosA*cosB
=cos(A-B)《1