Askor stated: I believed trigonometric substitution only work if there is offered a sq. root for example ##sqrt x^2 + 2 ##. No. Trig substitution is helpful When you have the sum or variation of squared phrases - they don't need to be within a square root. The short article https://gabletoppak.com/how-gable-top-pak-can-enhance-your-brand-and-customer-experience/