We have, (sin−1x)2 + (cos−1x)2 = (sin−1x+cos−1x)2 – 2 sin−1 x. cos−1 x = 4π2 - 2 sin−1x(2π−sin−1x) = 4π2 - π sin−1 x + 2 (sin−1)2 = 2 [(sin−1)2−2πsin−1x+8π2] = 2 [(sin−1x−4π)2+16π2] Thus, the least value is 2 (16π2) i.e. 8π2 and the greatest value is 2[(−2π−4π)2+18π2] i.e. 45π2