Askor explained: I assumed trigonometric substitution only perform if there is available a square root for instance ##sqrt x^2 + 2 ##. No. Trig substitution is useful if you have the sum or variation of squared conditions - they don't need to be within a sq. root. , or flat. https://gabletoppak.com/best-alternatives-to-plastic-water-bottles-in-kerala-for-a-greener-future/