Askor said: I assumed trigonometric substitution only do the job if there is out there a sq. root such as ##sqrt x^2 + 2 ##. No. Trig substitution is useful When you have the sum or variance of squared conditions - they don't need to be within a sq. root. https://gabletoppak.com/customized-mineral-water-bottles-and-packaged-drinking-water-the-future-of-sustainable-packaging-at-gabletop-pak/