Askor said: I believed trigonometric substitution only operate if there is on the market a square root including ##sqrt x^two + two ##. No. Trig substitution is helpful if you have the sum or change of squared terms - they needn't be within a square root. Photon 'time bins' and https://gabletoppak.com/water-in-a-sustainable-box-the-future-of-eco-friendly-hydration/