![You know that the sizes of all the angles in a triangle add up to 180 degrees. Justify that the sum of the sizes of all the angles in every quadrilateral is You know that the sizes of all the angles in a triangle add up to 180 degrees. Justify that the sum of the sizes of all the angles in every quadrilateral is](https://homework.study.com/cimages/multimages/16/interior_angles_of_quadrilateral-37837837326227872507.png)
You know that the sizes of all the angles in a triangle add up to 180 degrees. Justify that the sum of the sizes of all the angles in every quadrilateral is
![Question Video: Finding the Measure of an Angle in a Quadrilateral given the Other Angles' Measures | Nagwa Question Video: Finding the Measure of an Angle in a Quadrilateral given the Other Angles' Measures | Nagwa](https://media.nagwa.com/578173895294/en/thumbnail_l.jpeg)
Question Video: Finding the Measure of an Angle in a Quadrilateral given the Other Angles' Measures | Nagwa
![Three interior angles of a quadrilateral have measures of 111^{\circ}, 134^{\circ}, and 69^{\circ}. Find the fourth angle measure. | Homework.Study.com Three interior angles of a quadrilateral have measures of 111^{\circ}, 134^{\circ}, and 69^{\circ}. Find the fourth angle measure. | Homework.Study.com](https://homework.study.com/cimages/multimages/16/study_140921_quadrilateral018336149962482003110.png)