Askor stated: I thought trigonometric substitution only do the job if there is out there a sq. root for instance ##sqrt x^2 + 2 ##. No. Trig substitution is useful When you've got the sum or change of squared conditions - they don't need to be within a sq. root. https://gabletoppak.com/beyond-beverages-gable-top-cartons-the-versatile-customized-packaging-solution/