Answer:
\(m{\angle}D=60^{\circ}\)
Step-by-step explanation:
From the given figure, it can be seen that \(m{\angle}A=60^{\circ}\), \(m{\angle}B=60^{\circ}\), thus
From ΔABD, using the angle sum property, we have
\(m{\angle}A+m{\angle}B+m{\angle}D=180^{\circ}\)
⇒\(60^{\circ}+60^{\circ}+m{\angle}D=180^{\circ}\)
⇒\(120^{\circ}+m{\angle}D=180^{\circ}\)
⇒\(m{\angle}D=180^{\circ}-120^{circ}\)
⇒\(m{\angle}D=60^{\circ}\)
therefore, the measure of \({\angle}ADB\) is \(60^{\circ}\).
Hence, ΔABD is an equilateral triangle.
