Askor claimed: I assumed trigonometric substitution only do the job if there is available a sq. root which include ##sqrt x^two + two ##. No. Trig substitution is helpful In case you have the sum or variance of squared phrases - they need not be inside a square root. , https://gabletoppak.com/why-gable-top-cartons-are-making-a-splash-in-the-water-industry/