证明 (-cos(x))/(sin(x))=cot(x)

解答

证明

\frac{- cos ( x )}{sin ( x )} = cot (x)

假

求解步骤

\frac{- cos ( x )}{sin ( x )} = cot (x)

两侧不相等

对于

\frac{- cos ( x )}{sin ( x )} = cot (x)

代入

x = 1

\frac{- cos ( 1 )}{sin ( 1 )} = - 0.64209 \dots

\frac{- cos ( 1 )}{sin ( 1 )}

整理为小数形式

= - 0.64209 \dots

cot (1) = 0.64209 \dots

cot (1)

整理为小数形式

= 0.64209 \dots

两侧不相等

\Rightarrow 假

p ro v e sin (- \frac{2 π}{5}) = - sin (\frac{2 π}{5})

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

p ro v e sin^{2} (u) = \frac{( 1 - cos ( 2 u ) )}{2}

p ro v e 2 cos^{2} (x) - 1 = - 2 sin^{2} (x) + 1

p ro v e sin (x) = - 1 = sin (0) = - 1