Askor reported: I believed trigonometric substitution only perform if there is out there a sq. root including ##sqrt x^2 + 2 ##. No. Trig substitution is useful When you have the sum or variation of squared conditions - they don't need to be inside a square root. Gabletop Pak presents https://gabletoppak.com/why-gable-top-cartons-are-making-a-splash-in-the-water-industry/