Askor explained: I thought trigonometric substitution only operate if there is offered a square root for example ##sqrt x^2 + 2 ##. No. Trig substitution is useful For those who have the sum or big difference of squared terms - they don't need to be inside a square root. The https://gabletoppak.com/what-makes-gabletop-pak-cartons-a-better-choice-than-plastic-bottles/