Askor claimed: I believed trigonometric substitution only do the job if there is out there a sq. root for example ##sqrt x^2 + 2 ##. No. Trig substitution is helpful if you have the sum or difference of squared conditions - they need not be within a square root. This https://gabletoppak.com/why-gable-top-cartons-are-making-a-splash-in-the-water-industry/