In the figure, AFB and ADB are triangles. ABC, FEB and AED are straight lines. Given that ∠DEB\angle\text{DEB} is 79∘79^\circ and ∠DBC\angle\text{DBC} is 85∘85^\circ, find the value of ∠DAB+∠ADB+∠EAF+∠AFE\angle\text{DAB} + \angle\text{ADB} + \angle\text{EAF} + \angle\text{AFE}.

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Worked solution

8

1. Find the sum of $\angle\text{DAB}$ and $\angle\text{ADB}$ using the exterior angle of $\triangle ADB$.

In △ADB\triangle ADB, the exterior angle at BB is ∠DBC\angle\text{DBC}.
∠DAB+∠ADB=∠DBC=85∘\angle\text{DAB} + \angle\text{ADB} = \angle\text{DBC} = 85^\circ

2. Find $\angle\text{AEF}$ using vertically opposite angles.

Since AEDAED and FEBFEB are straight lines, ∠AEF\angle\text{AEF} and ∠DEB\angle\text{DEB} are vertically opposite angles.
∠AEF=∠DEB=79∘\angle\text{AEF} = \angle\text{DEB} = 79^\circ

3. Find the sum of $\angle\text{EAF}$ and $\angle\text{AFE}$ using the angle sum of $\triangle AFE$, and calculate the final total.

In △AFE\triangle AFE, the sum of angles is 180∘180^\circ.
∠EAF+∠AFE=180∘−∠AEF=180∘−79∘=101∘\angle\text{EAF} + \angle\text{AFE} = 180^\circ - \angle\text{AEF} = 180^\circ - 79^\circ = 101^\circ

Total sum =(∠DAB+∠ADB)+(∠EAF+∠AFE)= (\angle\text{DAB} + \angle\text{ADB}) + (\angle\text{EAF} + \angle\text{AFE})
=85∘+101∘=186∘= 85^\circ + 101^\circ = 186^\circ

Answer

186∘186^\circ

AI analysis — may contain mistakes.

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