∠A=60°,求sin(A+10°)[1-根号三tan(A-10°)]的值?
问题描述:
∠A=60°,求sin(A+10°)[1-根号三tan(A-10°)]的值?
答
sin(A+10°)[1-√3tan(A-10°)]=sin(A+10°)[1-√3sin(A-10°)/cos(A-10°)]=sin(A+10°)[cos(A-10°)--√3sin(A-10°)]/cos(A-10°)=2sin(A+10°)[1/2cos(A-10°)--√3/2sin(A-10°)]/cos(A-10°)=2sin(A+1...