Integral 1 Over T Squared Minus A Squared
1. The problem is to find the integral $$\int \frac{1}{t^2 - a^2} \, dt$$ where $a$ is a constant.
2. Recognize that the denominator can be factored using the difference of squares formula:
$$t^2 - a^2 = (t - a)(t + a)$$
3. Use partial fraction decomposition to express the integrand:
$$\frac{1}{t^2 - a^2} = \frac{1}{(t - a)(t + a)} = \frac{A}{t - a} + \frac{B}{t + a}$$
4. Multiply both sides by $(t - a)(t + a)$ to clear denominators:
$$1 = A(t + a) + B(t - a)$$
5. Expand the right side:
$$1 = A t + A a + B t - B a = (A + B) t + (A a - B a)$$
6. Equate coefficients of like terms:
- Coefficient of $t$: $A + B = 0$
- Constant term: $A a - B a = 1$
7. From $A + B = 0$, we get $B = -A$.
8. Substitute $B = -A$ into the constant term equation:
$$A a - (-A) a = A a + A a = 2 A a = 1$$
9. Solve for $A$:
$$A = \frac{1}{2 a}$$
10. Then $B = -\frac{1}{2 a}$.
11. Rewrite the integral using partial fractions:
$$\int \frac{1}{t^2 - a^2} \, dt = \int \left( \frac{1}{2 a (t - a)} - \frac{1}{2 a (t + a)} \right) dt$$
12. Integrate term by term:
$$= \frac{1}{2 a} \int \frac{1}{t - a} dt - \frac{1}{2 a} \int \frac{1}{t + a} dt$$
13. The integrals are natural logarithms:
$$= \frac{1}{2 a} \ln|t - a| - \frac{1}{2 a} \ln|t + a| + C$$
14. Combine the logarithms:
$$= \frac{1}{2 a} \ln \left| \frac{t - a}{t + a} \right| + C$$
**Final answer:**
$$\int \frac{1}{t^2 - a^2} \, dt = \frac{1}{2 a} \ln \left| \frac{t - a}{t + a} \right| + C$$