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Through-the-vertices-of-the-smaller-base-AB-of-the-trapezoid-ABCD-two-parallel-lines-are-drawn-intersecting-the-segment-CD-These-lines-and-the-trapezoid-s-diagonals-divide-it-into-seven-triangles-an




Question Number 16947 by Tinkutara last updated on 28/Jun/17
Through the vertices of the smaller  base AB of the trapezoid ABCD two  parallel lines are drawn, intersecting  the segment CD. These lines and the  trapezoid′s diagonals divide it into  seven triangles and a pentagon. Show  that the area of the pentagon equals  the sum of the areas of the three  triangles that share a common side  with the trapezoid.
$$\mathrm{Through}\:\mathrm{the}\:\mathrm{vertices}\:\mathrm{of}\:\mathrm{the}\:\mathrm{smaller} \\ $$$$\mathrm{base}\:{AB}\:\mathrm{of}\:\mathrm{the}\:\mathrm{trapezoid}\:{ABCD}\:\mathrm{two} \\ $$$$\mathrm{parallel}\:\mathrm{lines}\:\mathrm{are}\:\mathrm{drawn},\:\mathrm{intersecting} \\ $$$$\mathrm{the}\:\mathrm{segment}\:{CD}.\:\mathrm{These}\:\mathrm{lines}\:\mathrm{and}\:\mathrm{the} \\ $$$$\mathrm{trapezoid}'\mathrm{s}\:\mathrm{diagonals}\:\mathrm{divide}\:\mathrm{it}\:\mathrm{into} \\ $$$$\mathrm{seven}\:\mathrm{triangles}\:\mathrm{and}\:\mathrm{a}\:\mathrm{pentagon}.\:\mathrm{Show} \\ $$$$\mathrm{that}\:\mathrm{the}\:\mathrm{area}\:\mathrm{of}\:\mathrm{the}\:\mathrm{pentagon}\:\mathrm{equals} \\ $$$$\mathrm{the}\:\mathrm{sum}\:\mathrm{of}\:\mathrm{the}\:\mathrm{areas}\:\mathrm{of}\:\mathrm{the}\:\mathrm{three} \\ $$$$\mathrm{triangles}\:\mathrm{that}\:\mathrm{share}\:\mathrm{a}\:\mathrm{common}\:\mathrm{side} \\ $$$$\mathrm{with}\:\mathrm{the}\:\mathrm{trapezoid}. \\ $$

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