(1/2√2)∫{(x+√2)/x^2+√2x+1}dx-(1/2√2)∫{(x-√2)/x^2-√2x+1)}dx

がなぜ

(1/4√2)log{(x^2+√2x+1)/(x^2-√2x+1)}+(1/2√2){tan^-1(√2x+1)+tan^-1(√2x-1)}

になるのか教えてください！！