Finding Angle ACB: Triangle with 20° Angle Bisector Problem

The diagram shows right angle markers at points D on both sides BC. This indicates that AD is perpendicular to BC, making both $\angle ADB = \angle ADC = 90°$.

Look for the triangle where you know two angles and need to find the third. Here, in triangle ACD, we know $\angle CAD = 20°$ and $\angle ADC = 90°$, so we can find $\angle ACB$.

An angle bisector divides an angle into two equal parts. Since the diagram shows 20° in one part, the other part $\angle CAD$ is also 20°, making the total $\angle BAC = 40°$.

No, you need the angle bisector property to find that $\angle CAD = 20°$. Without this information, you wouldn't have enough known angles to use the triangle angle sum theorem.

The 20° shown in the diagram is $\angle BAD$ (or $\angle CAD$), not $\angle ACB$. These are completely different angles in the triangle. Always identify which angle the measurement refers to!