Askor reported: I thought trigonometric substitution only get the job done if there is accessible a sq. root which include ##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. https://gabletoppak.com/what-makes-gabletop-pak-cartons-a-better-choice-than-plastic-bottles/