Askor said: I assumed trigonometric substitution only do the job if there is out there a sq. root for example ##sqrt x^2 + two ##. No. Trig substitution is useful In case you have the sum or variation of squared terms - they needn't be within a square root. Photon https://gabletoppak.com/single-use-plastic-water-bottles-will-not-be-available-in-himachal-from-june-1-use-glass-bottles-and-dispensers-instead/