证明 2sin(x)-cot(x)=-cot(x)*2cot(x)

解答

证明

2 sin (x) - cot (x) = - cot (x) \cdot 2 cot (x)

假

求解步骤

2 sin (x) - cot (x) = - cot (x) \cdot 2 cot (x)

两侧不相等

对于

2 sin (x) - cot (x) = - cot (x) 2 cot (x)

代入

x = 1

2 sin (1) - cot (1) = 1.04084 \dots

2 sin (1) - cot (1)

整理为小数形式

= 1.04084 \dots

- cot (1) \cdot 2 cot (1) = - 0.82456 \dots

- cot (1) \cdot 2 cot (1)

整理为小数形式

= - 0.82456 \dots

两侧不相等

\Rightarrow 假

p ro v e 4 cos^{3} (a) - 3 cos (a) = cos (3 a)

p ro v e sin^{2} (θ) + (\frac{1}{2})^{2} = 1

p ro v e sin (θ) (cot (θ) + tan (θ)) = tan (θ)

p ro v e - csc^{2} (x) = \frac{sec ( x )}{2 sin ( x )}

p ro v e \frac{sec ( x ) cos ( x )}{cot ( x )} = tan (x)