Askor stated: I assumed trigonometric substitution only work if there is offered a square root like ##sqrt x^2 + two ##. No. Trig substitution is helpful When you have the sum or distinction of squared terms - they needn't be inside a sq. root. Gable roofs are straightforward and simple https://gabletoppak.com/what-makes-gabletop-pak-cartons-a-better-choice-than-plastic-bottles/