Askor stated: I thought trigonometric substitution only operate if there is on the market a sq. root for instance ##sqrt x^2 + 2 ##. No. Trig substitution is useful When you've got the sum or variance of squared phrases - they don't need to be inside of a square root. https://gabletoppak.com/customized-mineral-water-bottles-and-packaged-drinking-water-the-future-of-sustainable-packaging-at-gabletop-pak/