y=√x在点(1,1)处的曲率。解:y'=1/(2√x); y'(1)=1/2; y''=-1/(4x√x); y''(1)=-1/4;曲率k=∣y''/(1+y'2)^(3/2)∣, k(1)=∣(-1/4)/(1+1/4)^(3/2)∣=2/(5√5) ∴曲率半径R(1)=1/k=(5/2)√5.
f(x) = (x+1)/x
f(2) = (2+1)/2 = 3/2
f(1) = (1+1)/1 = 2
[f(2)-f(1) ]/(2-1) = -1/2
f'(x)= -1/x^2
-1/x^2 = -1/2
x^2 =2
x=√2
函数f(x)=(x+1)/x,则f(x)在[1,2]上满足拉格朗日中值定理的ξ=√2