证明 sin(a-b)=sin(a)cos(b)-cos(a)sin(b)

解答

证明

sin (a - b) = sin (a) cos (b) - cos (a) sin (b)

真

求解步骤

sin (a - b) = sin (a) cos (b) - cos (a) sin (b)

使用角差恒等式:

sin (s - t) = sin (s) cos (t) - cos (s) sin (t)

\Rightarrow 真

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

p ro v e cos (x) = sin (x) tan^{2} (x) cot^{3} (x)

p ro v e 7 sin (7 π - x) = 7 sin (x)

p ro v e sin (- θ) + cos (- θ) = cos (θ) - sin (θ)

p ro v e 4 sec (y) cos (y) = 4