Step 1 :Set \(u = 7+9t\), then \(du = 9dt\).
Step 2 :Adjust the integral to account for this substitution.
Step 3 :The integral of the function \(\cos(7 + 9t)\) with respect to \(t\) is \(\frac{\sin(7 + 9t)}{9}\).
Step 4 :Add the constant of integration \(C\) to the result.
Step 5 :The indefinite integral of \(\cos(7 + 9t)\) with respect to \(t\) is \(\boxed{\frac{\sin(7 + 9t)}{9} + C}\).