展开 [(t)cos(4t)U(t-(pi/4))]

解答

展开

[(t) cos (4 t) U (t - (\frac{π}{4}))]

t^{2} U cos (4 t) - \frac{π t U cos ( 4 t )}{4}

求解步骤

(t) cos (4 t) U (t - (\frac{π}{4}))

去除括号:

(a) = a

= t cos (4 t) U (t - \frac{π}{4})

= t U cos (4 t) (t - \frac{π}{4})

使用分配律:

a (b - c) = ab - a c

a = t cos (4 t) U, b = t, c = \frac{π}{4}

= t cos (4 t) U t - t cos (4 t) U \frac{π}{4}

= tt U cos (4 t) - \frac{π}{4} t U cos (4 t)

化简

tt U cos (4 t) - \frac{π}{4} t U cos (4 t) : t^{2} U cos (4 t) - \frac{π t U cos ( 4 t )}{4}

= t^{2} U cos (4 t) - \frac{π t U cos ( 4 t )}{4}

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