∫1/(3-cosx) dx=∫1/[2+2(sin0.5x)^2]dx=∫1/[1+(sin0.5x)^2]d(0.5x)=∫(csc0.5x)^2/[(csc0.5x)^2+1]d(0.5x)=-∫1/[(cot0.5x)^2+2]d(cot0.5x)=-(1/√2)arctan(cot0.5x/√2)+C
√2/2*arctan(√2*tan(x/2))
