For each integral, decide whether it can be evaluated using only the power, sum, and constant multiple rules; a linear substitution; or the logarithmic rule \(\int\frac{g'(x)}{g(x)}\,dx=\ln|g(x)|+C\). Evaluate every integral that can be handled by those methods.
1. \(\int_{1}^{2}\frac{x^2+1}{x^2} \, dx\)
2. \(\int_{0}^{1}\frac{3x^2}{x^3+1} \, dx\)
3. \(\int_{0}^{2}e^{0.5x} \, dx\)
4. \(\int_{1}^{2}\ln(x) \, dx\)
5. \(\int_{0}^{1}\frac{1}{x^2+1} \, dx\)
Hints
- Rewrite the rational expression in 1 as a sum of powers of \(x\).
- In 2, compare the numerator with the derivative of the denominator.
- In 3, account for the derivative of \(0.5x\).
- For 4 and 5, ask whether any of the specifically listed antiderivative patterns applies.
Solution
1. For 1, use the power, sum, and constant multiple rules. Rewrite the integrand as \(1+x^{-2}\). Then \([x-\frac{1}{x}]_1^2=\frac{3}{2}\).
2. For 2, use the logarithmic rule with \(g(x)=x^3+1\), since \(g'(x)=3x^2\). Thus \([\ln(x^3+1)]_0^1=\ln(2)\).
3. For 3, use a linear substitution, or account directly for the inner derivative. An antiderivative is \(2e^{0.5x}\), so \([2e^{0.5x}]_0^2=2e-2\).
4. The fourth integral cannot be evaluated using only the listed methods; a standard method is integration by parts.
5. The fifth integral cannot be evaluated using only the listed methods; its antiderivative involves \(\arctan(x)\).
Answer
1. Power, sum, and constant multiple rules: \(\frac{3}{2}\)
2. Logarithmic rule: \(\ln(2)\)
3. Linear substitution: \(2e-2\)
4. Not evaluable using only the listed methods.
5. Not evaluable using only the listed methods.