展开 sin((n+1/2)pi)

解答

展开

sin ((n + \frac{1}{2}) π)

(- 1)^{n}

求解步骤

sin ((n + \frac{1}{2}) π)

乘开

(n + \frac{1}{2}) π : πn + \frac{π}{2}

= sin (πn + \frac{π}{2})

使用三角恒等式改写

= cos (πn)

使用基本三角恒等式:

cos (nπ) = (- 1)^{n}

= (- 1)^{n}

e x p an d (3 t - 3) e^{\frac{t + 2}{3}}

e x p an d \frac{π ^{2}}{4} + (- 1, - 1 + π) (x, y + \frac{π}{2})

e x p an d \frac{7 x + 6}{x ( x + 3 )}

e x p an d (E x p an d,) (x - 4) (x - 2)

e x p an d (cot (y) + x^{2}) d x - x csc^{2} (y) d y