let u= sinx du = cosx dx ∫cosx/√(2+cos2x) dx =∫cosx/√[3-2(sinx)^2] dx =∫du/√(3-2u^2) let u= (1/2)√6 .sint du = (1/2)√6 .cost dt ∫cosx/√(2+cos2x) dx =∫du/√(3-2u^2) =(1/2)√2 ∫ dt =(√2/2) t + C =(√2/2)arcsin[(√6/3)sinx] + C where 。