Askor claimed: I thought trigonometric substitution only work if there is out there a sq. root like ##sqrt x^two + 2 ##. No. Trig substitution is useful Should you have the sum or variation of squared terms - they needn't be inside a sq. root. This is supported by a https://gabletoppak.com/bioplastics-greenwashing-or-genuine-solution-the-truth-behind-the-hype/