求直线和圆的交点时,就是解一元二次方程,下列说法正确的是:
A. 一元二次方程有唯一实数解,则直线和圆相切。
B. 一元二次方程有两个实数解,则直线和圆相割。
C. 一元二次方程无实数解,则直线和圆相离。
D. 以上说法都正确。
A __________ is a shaft to which a cam is fastened.
A. camshaft
B. crankshaft
C. piston
D. bearing
Sliding friction between the _________ of the cam and the cam follower is considerable.
A. inside
B. front
C. surface
D. back