Rhombus 36

Rhombus ABCD with side 8 cm long has diagonal BD 11.3 cm long. Find angle DAB.

Correct answer:

α =  89.8612 °

Step-by-step explanation:

a=8 cm u=11.3 cm  a=AB=BC=CD=DA α = ∢DAB  u2 = a2 + a2 −2⋅ a⋅ a⋅ cos α  A=arccos(2⋅ a22⋅ a2−u2​)=arccos(2⋅ 822⋅ 82−11.32​)≐1.5684 rad  α=A→  °=A⋅ π180​   °=1.5684⋅ π180​   °=89.861  °=89.8612∘=89°51′40"

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