证明 tan(2x)-sin(2x)=tan(2x)sin(2x)

解答

证明

tan (2 x) - sin (2 x) = tan (2 x) sin (2 x)

假

求解步骤

tan (2 x) - sin (2 x) = tan (2 x) sin (2 x)

两侧不相等

对于

tan (2 x) - sin (2 x) = tan (2 x) sin (2 x)

代入

x = 1

tan (2 \cdot 1) - sin (2 \cdot 1) = - 3.09433 \dots

tan (2 \cdot 1) - sin (2 \cdot 1)

整理为小数形式

= - 3.09433 \dots

tan (2 \cdot 1) sin (2 \cdot 1) = - 1.98685 \dots

tan (2 \cdot 1) sin (2 \cdot 1)

整理为小数形式

= - 1.98685 \dots

两侧不相等

\Rightarrow 假

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

p ro v e \frac{cos ( β )}{1 - sin ( β )} = sec (β) + tan (β)

p ro v e tan^{2} (y) - sin^{2} (y) = tan^{2} (y) sin^{2} (y)

p ro v e sin (θ) (1 + cot^{2} (θ)) = csc (θ)

p ro v e 5 + cot^{2} (x) = 4 + csc^{2} (x)