We are integrating f(x) = 9cos(9x) + 3x²:
a) Apply the sum rule
b) Calculate each antiderivative
<u>First integral</u>
1. Take out the constant
2. Apply u-substitution, where u is 9x
3. Take out the constant (again)
4. Take the common integral of cos, which is sin
5. Substitute the original function back in for u and simplify
6. Always remember to add an arbitrary constant, C, at the end
<u>Second integral</u>
1. Take out the constant
2. Apply the power rule, , where <em>a</em> is your exponent
⇒
3. Add the arbitrary constant
c) Add the integrals
sin(9x) + C + x³ + C = sin(9x) + x³ + C
Notice the two arbitrary constants. Since we do not know what either constant is, we can combine them into one arbitrary constant.
<h3>Answer:</h3>F(x) = sin(9x) + x³ + C