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#e68caffa-f120-460b-a32a-9a934eaecca6中等解答题二倍角公式三角函数与三角恒等变换

16. (2022秋•和平区校级月考)已知f(α)=sin(πα)cos(2πα)sin(α+3π2)cos(απ)cos(α+7π2)f(\alpha )=\frac{\sin ({\pi -\alpha })\cos ({2\pi -\alpha })\sin ({-\alpha +\frac{3\pi }{2}})}{\cos ({-\alpha -\pi })\cos ({-\alpha +\frac{7\pi }{2}})}
(1)化简f(α)f(\alpha )
(2)若α\alpha是第三象限角,且cos(α3π2)=15\cos ({\alpha -\frac{3\pi }{2}})=\frac{1}{5},求f(α)f(\alpha )
(3)若角AAΔABC\Delta ABC的内角,且f(A)=35f(A)=\frac{3}{5},求tanAsinA\tan A-\sin A的值.