Askor mentioned: I thought trigonometric substitution only work if there is accessible a sq. root for instance ##sqrt x^2 + 2 ##. No. Trig substitution is useful if you have the sum or variation of squared conditions - they don't need to be within a sq. root. Find out a https://gabletoppak.com/free-water-advertising-a-sustainable-and-emotional-path-to-powerful-brand-recognition/