(sinx+cosx)/(sinx-cosx)=3 求sin^2(x)+sinxcosx
问题描述:
(sinx+cosx)/(sinx-cosx)=3 求sin^2(x)+sinxcosx
答
sinx+cosx=3sinx-3cosx
2sinx=4cosx
tanx=2
cosx^2=1/(1+tanx^2)=1/5
sinx^2=1-cosx^2=4/5
sinxcosx=tanxcosx^2=2/5
sinx^2+sinxcosx=4/5+2/5=6/5