It is is a parallelogram, hence we have to face sides equal in length and the opposite angles are also the same. From the given above we have: ab=14 and its opposite side cd=14 bc=20 and its opposite side da=20
Solving for the diagonal measurement bd, we have consecutive angles are equal to 180° ∠A+∠B=180° ∠A=180°-54° ∠A=126° , ∠B=54° ,∠C=126° and ∠D=54° bd²=ab²+da²-2(ab)(da)cos126° bd²=14²+20²-2*14*20cos126° bd=30.42 unit
Solving for the angle dbc, we have cos dbc=bc²+bd²-cd²/a*bc*bd cos dbc=20²+30.42²-14²/2*20*30.42 dbc=21.76°
