Askor explained: I thought trigonometric substitution only work if there is out there a sq. root for instance ##sqrt x^2 + two ##. No. Trig substitution is useful When you've got the sum or variance of squared terms - they needn't be within a square root. Photon 'time bins' and https://gabletoppak.com/aseptic-tetra-pak-vs-non-aseptic-gable-top-choosing-the-right-carton-for-your-needs/