Complete the Square for Integrals

In calculus, integrating rational functions often requires completing the square in the denominator to match standard integration formulas like arctan.

Complete the Square (Integrals)

∫ 1 / (a(x-h)² + k) dx
1 ax² + bx + c dx a(x - h)² + k

Calculus Applications

∫ 1/(ax² + bx + c) dx

When faced with an integral of the form ∫ 1/(ax² + bx + c) dx, standard substitution usually fails. By completing the square, you can transform the denominator into the form u² + a², which allows for trigonometric substitution.

The Arctan Rule

∫ 1/(x²+a²) dx = (1/a)arctan(x/a)

The most common result of completing the square in an integral denominator is the arctangent function. The standard formula is ∫ 1/(x² + a²) dx = (1/a)arctan(x/a) + C.

Handling Roots

∫ 1/√(u²+a²) dx → arcsin / ln

This technique is also essential when the quadratic is under a square root in the denominator: ∫ 1/√(ax² + bx + c) dx. Completing the square transforms this into an arcsin or natural log form, depending on the signs.

Complete the Square Calculators

Specialized tools for every completing the square scenario — pick the one that matches your problem.

Frequently Asked Questions