Askor explained: I thought trigonometric substitution only do the job if there is obtainable a sq. root for example ##sqrt x^two + two ##. No. Trig substitution is useful In case you have the sum or variance of squared terms - they don't need to be inside of a sq. https://gabletoppak.com/from-plastic-bottles-to-gabletop-cartons-a-step-toward-solving-the-plastic-pollution-crisis/