1 + 4x²/(1-x²)² = ((1-x²)²+4x²)/(1-x²)² = (1-2x²+x^4+4x²)/(1-x²)² = (1+2x²+x^4)/(1-x²)²
= (1+x²)²/(1-x²)²
√(1 + 4x²/(1-x²)²) = (1+x²)/(1-x²) = - (x²+1)/(x²-1) = - ((x²-1) + 2)/(x²-1) = -1 - 2/(x²-1)
= -1 - (1/(x-1) - 1/(x+1)) = -1 - 1/(x-1) + 1/(x+1)
∫ √(1 + 4x²/(1-x²)²) dx = ∫ (-1 - 1/(x-1) + 1/(x+1)) dx = -x - ln |x-1| + ln |x+1|
Nu är det bara att sätta in gränserna.