Question

有关三角函数的题目、、、help!

Answer 1

sinx^2+2sinxcosx+3cosx^2

=(sinx^2+2sinxcosx+3cosx^2)/(sinx^2+cosx^2) //sinx^2+cosx^2=1

=(tanx^2+2tanx+3)/(tanx^2+1) //分子、分母同除以cosx^2

=(m^2+2m+3)/(m^2+1) //tanx=m代入