作业帮tanθ/(1+〖tan〗^2 θ)≡sinθcosθ(1-(〖tan〗^(2 ) 60)/sin30)〖cos〗^245sinθ=7/25 find the value of 3tanθ-1/cosθ by using 勾股定理(tanθ/cosθ+sinθ/(〖cos〗^2 θ ))×〖cos〗^2θCos(40-3θ)=sin(7θ+2)If tanA=5/3 find the value of 4s
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tanθ/(1+〖tan〗^2 θ)≡sinθcosθ(1-(〖tan〗^(2 ) 60)/sin30)〖cos〗^245sinθ=7/25 find the value of 3tanθ-1/cosθ by using 勾股定理(tanθ/cosθ+sinθ/(〖cos〗^2 θ ))×〖cos〗^2θCos(40-3θ)=sin(7θ+2)If tanA=5/3 find the value of 4s
tanθ/(1+〖tan〗^2 θ)≡sinθcosθ
(1-(〖tan〗^(2 ) 60)/sin30)〖cos〗^245
sinθ=7/25 find the value of 3tanθ-1/cosθ by using 勾股定理
(tanθ/cosθ+sinθ/(〖cos〗^2 θ ))×〖cos〗^2θ
Cos(40-3θ)=sin(7θ+2)
If tanA=5/3 find the value of 4sinA/(3sinA-cosA) by using 三角恒等式
看不惯可以看图片
tanθ/(1+〖tan〗^2 θ)≡sinθcosθ(1-(〖tan〗^(2 ) 60)/sin30)〖cos〗^245sinθ=7/25 find the value of 3tanθ-1/cosθ by using 勾股定理(tanθ/cosθ+sinθ/(〖cos〗^2 θ ))×〖cos〗^2θCos(40-3θ)=sin(7θ+2)If tanA=5/3 find the value of 4s
1.左边上下同时乘以cos^2θ 就行了
2.往里套数...
3.把tanθ变形成sinθ/cosθ,cos^2θ=1-sin^2θ求出cosθ,带入即可
4.把tanθ变形成sinθ/cosθ,就变成（2sinθ/cos^2 θ ）× cos^2θ =2sinθ
5.不会
6.上下同时除以cosA ,这样分子分母就都由tanA构成了,带入即可