Practice!

Sample Problem

The figure is not drawn to scale.

∠CBD = 90° and ∠ABC = 135°. What is ∠ABD ?

∠ABD = °.

Solution

∠ABC , ∠CBD and ∠ABD are angles at a point.

∠ABC + ∠CBD + ∠ABD = 360°.

∠ABD = 360° − ∠ABC − ∠CBD

= 360° − 135° − 90° = 135°.

∴∠ABD = 135°.