IKMC 2011 - Grades 11-12 - Paper 01 - Self-study Question 15

Question 15

A rear-window wiper has blade RW and rod OR of equal length, joined at fixed angle α. It rotates about O and clears the shaded area. Find angle β between the right-hand edge of the cleared area and the tangent to its upper curved edge.

Question illustration

$(3\pi-\alpha)/2$
$\pi-\alpha/2$
$3\pi/2-\alpha$
$\pi/2+\alpha$
$\pi+\alpha/2$