The perimeter of a rhombus is 40 cm, its measure of an angle is 60 degree, then its area is?

50 \(\sqrt {3}\) cm²

\(\angle\)A = 60° ⇒ \(\angle\)C = 60°

\(\angle\)B = \(\angle\)D = \(\frac{360° - 120°}{2}\) = 120°

\(\angle\)ABD = \(\angle\)ADB = 60°

ΔABD is equilateral Δ ; [ side = \(\frac{40}{4}\) = 10 cm]

Area of rhombus = 2 × area of ΔABD

                         = 2 × \(\frac{\sqrt {3}}{4}\)(10)²

                          = 50\(\sqrt {3}\)cm²