Askor claimed: I thought trigonometric substitution only function if there is out there a square root for example ##sqrt x^2 + two ##. No. Trig substitution is helpful When you have the sum or big difference of squared terms - they don't need to be inside of a square root. https://gabletoppak.com/how-gable-top-pak-and-paper-bottles-lead-in-sustainable-beverage-packaging/