【单选题】A motor drives a shaft at f=10 Hz and delivers P= 35 kW of power. The allowable shear stress in the shaft is 45 MPa. The minimum diameter of the shaft is approximately:【图片】
【多选题】If a point x* is a minimum of the function f(x) under the constrained condition g(x)=0, the first-order necessary for the condition extremum includes ( )
A.
f(x*)=0
B.
g(x*)=0
C.
▽f(x*)=0 [the gradient of the function f at the point x* is equal to zero vector]