1.已知A,B均为锐角,且cos(A+B)=sin(A-B),则tanA=_____
问题描述:
1.已知A,B均为锐角,且cos(A+B)=sin(A-B),则tanA=_____
2.(sin7+cos15sin8)/cos7-sin15sin8的值为多少(角度为角度制!)
答
1. cos(A+B)=cosAcosB-sinAsinB sin(A-B)=sinAcosB-sinBcosA cosAcosB-sinAsinB=sinAcosB-sinBcosA cosA(cosB+sinB)=sinA(cosB+sinB) tanA=12. sin7=sin(15-8)=sin15cos8-sin8cos15 cos7=cos(15-8)=co...