Q. The maximum efficiency of spiral gears is (where $$\theta $$ = Shaft angle and $$\varphi $$ = Friction angle)

• (A) sin(θ+φ)+1 cos(θ−φ)+1
• (B) cos(θ−φ)+1 sin(θ+φ)+1
• (C) cos(θ+φ)+1 cos(θ−φ)+1
• (D) cos(θ−φ)+1 cos(θ+φ)+1