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Goal: Find the integral - 912 cos(2x3) dx using the technique of u-substitution. 1. Let u 27-3 Then du 1212 dx. 2. Performing the substitution yields the following integral in terms of u: du, which in terms of u has the antiderivative +C. 3. Therefore, in terms of r, - 9x cos(2x ) dx equals 3 sin ( 223 2