Find the formula, in terms of K, for the area of a regular octagon with apothem K and side of 10. A =

Amistre64 started tohelp me but i couldn't find the apothem formula. He says it should be A=8(k*10/2)

Question

Find the formula, in terms of K, for the area of a regular octagon with apothem K and side of 10. A = 

Amistre64 started tohelp me but i couldn't find the apothem formula. He says it should be A=8(k*10/2)

anonymous · Answer

Area is $ \frac12 pa = \frac12 \times  80\times k = 40k ,$ 

NOTE: $p$ = perimeter and $a$ is the apothem

phi · Answer

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the octagon can be broken up into 8 identical triangles 
apothem is just a fancy word for the altitude of the triangle
so find the area of one triangle and multiply by 8