In Calculus II we learn the wretched “Trigonometric substitution” and it can be hard to remember them. I came up with this little pneumonic device to help me out. Is it good? Not at all. Did it help? Yes, it did.

a^2-x^2 = sin^2x: Sine gets the mine.

a^2+x^2 = tan^2x: Remember the A in tAngent and the A in Add. Taddgent.

x^2-a^2 = sec^2x: She cant keep that constant = secant keep that constant.

These are stupid but I hope that they help.