1. The problem statement, all variables and given/known data f(x) = sqrt(1 - x) a = 0 Approximate sqrt(0.9). 2. Relevant equations L(x) = f'(a)(x - a) + f(a) 3. The attempt at a solution I understand that linear approximation is finding the equation of a line of a point tangent to a function. But now this question is asking me to approximate the value of sqrt(0.9), which I assume means without the use of a calculator. The given function is sqrt(1 - x) and a = 0. So f(0) = 1 and f'(0) = -1/2. Therefore the equation of the line tangent at (0,1) of this function is -x/2 + 1. How does this have anything to do with finding the value of sqrt(0.9)?