Askor mentioned: I assumed trigonometric substitution only do the job if there is out there a square root for example ##sqrt x^two + two ##. No. Trig substitution is helpful When you've got the sum or variance of squared conditions - they need not be inside a square root. Entrance https://gabletoppak.com/glass-bottles-for-beer-soda-and-even-water-found-to-contain-toxic-levels-of-cancer-linked-microplastics-than-plastic-bottles-study-says/