Given that ABCD is a parallelogram, the sum of its interior angles is:
360°
A parallelogram is a rectilinear two-dimensional figure with four sides whose opposite sides are parallel. See the image attached.
The sum of the exterior angles of any Triangle or any polygon is 360°. Hence, the sum of the exterior angles of CHFE (a polygon) is 360°.
The sides that are parallel to CE are:
FH
AD and
The side that are perpendicular to CE is side side HH, hence we can state that:
CE ⊥ EH, because both lines intersect each other at right angles.
Because the sum of angles in a triangle is 180° and we already have ∠CEH to be equal to ∠90° hence,
∠C + ∠H? = 180° - 90°
= 90°
The measure of the exterior angles of a regular pentagon is 72°
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