Askor mentioned: I thought trigonometric substitution only perform if there is out there a sq. root for instance ##sqrt x^2 + 2 ##. No. Trig substitution is useful Should you have the sum or variation of squared phrases - they don't need to be inside a sq. root. Front Gable: https://gabletoppak.com/how-gable-top-pak-and-paper-bottles-lead-in-sustainable-beverage-packaging/