Askor reported: I thought trigonometric substitution only get the job done if there is accessible a sq. root such as ##sqrt x^2 + two ##. No. Trig substitution is useful When you've got the sum or difference of squared terms - they needn't be within a square root. Entrance Gable: https://gabletoppak.com/gabletop-pak-leading-the-way-as-milk-carton-manufacturers-in-india/