Askor reported: I thought trigonometric substitution only do the job if there is offered a square root such as ##sqrt x^2 + 2 ##. No. Trig substitution is helpful Should you have the sum or difference of squared conditions - they don't need to be inside of a sq. root. https://gabletoppak.com/sustainable-liquid-soap-packaging-why-gabletop-cartons-are-the-eco-friendly-choice/