已知tan(a+π/4)=1/3,求tana的值2)求2sin^2a-sin(π-a)sin(π/2-a)+sin^2(3π/2+a)
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已知tan(a+π/4)=1/3,求tana的值2)求2sin^2a-sin(π-a)sin(π/2-a)+sin^2(3π/2+a)
已知tan(a+π/4)=1/3,求tana的值
2)求2sin^2a-sin(π-a)sin(π/2-a)+sin^2(3π/2+a)
已知tan(a+π/4)=1/3,求tana的值2)求2sin^2a-sin(π-a)sin(π/2-a)+sin^2(3π/2+a)
1、
(tana+tanπ/4)/(1-tanatanπ/4)=1/3
(tana+1)/(1-tana)=1/3
3tana+3=1-tana
tana=-1/2
2、
sina/cosa=tana=-1/2
cosa=-2sina
代入sin²a+cos²a=1
sin²a=1/5
cos²a=4/5
sinacosa=sina(-2sina)=-2sin²a=-2/5
原式=2sin²a-sinacosa+cos²a
=2/5+2/5+4/5
=8/5
而我