true or false:all parallelograms have opposite angles that are supplementary

http://www.ies.co.jp/math/products/geo1/applets/para/para.html

http://www.mathsisfun.com/geometry/supplementary-angles.html

What do you think the answer is?

FALSE

True. All parallelograms have opposite angles that are supplementary, meaning their measures add up to 180 degrees.

True.

To confirm this statement, we can refer to the definition of a parallelogram. A parallelogram is a quadrilateral with two pairs of parallel sides. Since opposite sides of a parallelogram are parallel, this means that opposite angles will be congruent.

In a parallelogram, adjacent angles are supplementary, meaning that the sum of two adjacent angles is 180 degrees. This can be proven using the fact that opposite sides are parallel. If we draw a transversal (a line that intersects two parallel lines), we can observe that the alternate interior angles are congruent. And since alternate interior angles are supplementary, this implies that adjacent angles in a parallelogram are supplementary.

Therefore, since adjacent angles in a parallelogram are supplementary, it follows that opposite angles (which are made up of adjacent angles on opposite sides) in a parallelogram are also supplementary.