2015 · Q57
ABCD is a parallelogram with AB and AD as adjacent sides. If ∠A=60° and AB=2AD, then the diagonal BD will be equal to
Elementary MathematicsGeometry: Lines, Angles and Triangles
- A{2} AD
- B{3} AD
- C2AD
- D3AD
Explanation
BD^2 = AB^2 + AD^2 - 2*AB*AD*cos60 = 4AD^2 + AD^2 - 2AD^2 = 3AD^2, so BD = sqrt(3)*AD. Hence option (b).