已知tan(a+兀⼀4)=1⼀2且-兀⼀2<a<0则(

已知tan(a+兀/4)=1/2且-兀/2<a<0则(2sina∧2+sin2a)/sin(a-兀/4)的值
2025-03-11 00:27:31
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回答1:

∵tan(a+兀/4)=1/2

∴(2sin^2a+sin2a)/sin(a-兀/4)

=(2sin^2a+2sinacosa)/(sinacosπ/4-cosasinπ/4)
=2sina(sina+cosa)/.[√2/2(sina-cosa)]
=2√2(sina+cosa)/(sina-cosa)
=2√2(sina/cosa+1)/(sina/cosa-1)
=-2√2(1+tana)/(1-tana)
=-2√2(tanπ/4+tana)/(1-tanπ/4tana)
=-2√2tan(a+π/4)
=-2√2*1/2
=-√2