Askor claimed: I thought trigonometric substitution only do the job if there is offered a square root for instance ##sqrt x^2 + 2 ##. No. Trig substitution is useful In case you have the sum or distinction of squared conditions - they don't need to be within a sq. root. https://gabletoppak.com/water-in-a-sustainable-box-the-future-of-eco-friendly-hydration/