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