Parallelogram 65954

In the parallelogram ABCD AB = 8, BC = 5, BD = 7. Calculate the magnitude of the angle α = ∠DAB (in degrees).

Correct answer:

α =  60 °

Step-by-step explanation:

AB=8 BC=5 BD=7  AD=BC=5  BD2  = AB2+AD2  2 AB AD   cos α  c=2 AB ADAB2+AD2BD2=2 8 582+5272=21=0.5  α=π180°arccosc=π180°arccos0.5=60

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