Evaluate the Integral by Making the Given Substitution $$\int \cos 3 x d x , u = 3 x$$

Q18: Approximate the area under the curve

Q19: Find the indefinite integral. <span

Q20: Evaluate the Riemann sum for

Q21: Find the derivative of the function.

Q22: <span class="ql-formula" data-value="\text { Find a function

Q24: Find the indefinite integral. <span

Q25: The table gives the values of

Q26: <span class="ql-formula" data-value="\text { Find the interval

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Q28: Find the indefinite integral.<br> <span class="ql-formula"