Askor said: I assumed trigonometric substitution only get the job done if there is out there a square root for example ##sqrt x^2 + 2 ##. No. Trig substitution is useful When you have the sum or difference of squared phrases - they need not be within a sq. root. https://gabletoppak.com/choosing-between-gable-top-packaging-and-plastic-bottles-for-your-beverage-business/