=(2sin²a-3sinacosa-5cos²a)/(sin²a+cos²a) (sin²a+cos²a)哪来的?
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![=(2sin²a-3sinacosa-5cos²a)/(sin²a+cos²a) (sin²a+cos²a)哪来的?](/uploads/image/z/10396807-7-7.jpg?t=%3D%282sin%26%23178%3Ba-3sinacosa-5cos%26%23178%3Ba%29%2F%28sin%26%23178%3Ba%2Bcos%26%23178%3Ba%EF%BC%89+%28sin%26%23178%3Ba%2Bcos%26%23178%3Ba%EF%BC%89%E5%93%AA%E6%9D%A5%E7%9A%84%3F)
=(2sin²a-3sinacosa-5cos²a)/(sin²a+cos²a) (sin²a+cos²a)哪来的?
=(2sin²a-3sinacosa-5cos²a)/(sin²a+cos²a) (sin²a+cos²a)哪来的?
=(2sin²a-3sinacosa-5cos²a)/(sin²a+cos²a) (sin²a+cos²a)哪来的?
(sin²a+cos²a)=1
任何代数式除以1不变
2sin²a-3sinacosa-5cos²a
=(2sin²a-3sinacosa-5cos²a)/1
=(2sin²a-3sinacosa-5cos²a)/(sin²a+cos²a)