已知θ为锐角,且tan²θ+√2tanθ-4=0,求3sin²θ-2cos²θ／3sin²θ+2cos²θ

已知θ为锐角,且tan²θ+√2tanθ-4=0,求3sin²θ-2cos²θ／3sin²θ+2cos²θ
已知θ为锐角,且tan²θ+√2tanθ-4=0,求3sin²θ-2cos²θ／3sin²θ+2cos²θ

已知θ为锐角,且tan²θ+√2tanθ-4=0,求3sin²θ-2cos²θ／3sin²θ+2cos²θ
θ为锐角
tanθ>0
tan²θ+√2tanθ-4=0
tan²θ+√2tanθ+1/2=4+1/2=9/2
(tanθ+√2/2)²=9/2
tanθ+√2/2=±3√2/2
tanθ=±3√2/2-√2/2
tanθ=√2 tanθ=-2√2(舍去)
3sin²θ-2cos²θ／3sin²θ+2cos²θ
=cos²θ(3tan²θ-2)/cos²θ(3tan²θ+2)
=(3*2-2)/(3*2+2)
=4/8
=1/2

请问这是几年级的？？？