设a,b,x,y属于R,且a^2+b^2=1,x^2+y^2=1,试证|ax+by

问题描述:

设a,b,x,y属于R,且a^2+b^2=1,x^2+y^2=1,试证|ax+by

数学人气:947 ℃时间:2020-10-02 03:38:15
优质解答
a=sinA,b=cosA
x=sinB,y=cosB
ax+by
=sinAsinB+cosAcosB
=cos(A-B)
-1|cos(A-B)||ax+by|

a=sinA,b=cosA
x=sinB,y=cosB
ax+by
=sinAsinB+cosAcosB
=cos(A-B)
-1|cos(A-B)||ax+by|