Positive SSL
1 一螺旋線旋繞於一圓柱表面,此圓柱之直徑為D,此螺旋線之導程為L,螺旋角(helix angle)為30°,導程角(lead angle)為60°,則下列何者正確?
A tan30° = `L/(πD)`
B tan60° = `L/(πD)`
C L =πD cot 30°
D L =πD cos 30°