展开 U(t-pi)cos(3t)

解答

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U (t - π) cos (3 t)

U t cos (3 t) - π U cos (3 t)

求解步骤

U (t - π) cos (3 t)

= U cos (3 t) (t - π)

使用分配律:

a (b - c) = ab - a c

a = U cos (3 t), b = t, c = π

= U cos (3 t) t - U cos (3 t) π

= U t cos (3 t) - π U cos (3 t)

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