Question 1037163
The sum of the measures of the interior angles of any quadrilateral is 360.
Take any quadrilateral, convex or non, draw a line through it to break it into 2 triangles. Then the laws of triangles applies:
"the sum of the interior angles of ANY triangle is 180 degrees"
Since you split the quadrilateral into 2 triangles and each triangle is 180 degrees, 2*180 = 360
Attached is a picture for you to print and practice how you would draw a line to split a convex and a non-convex quadrilateral into two triangles:
*[illustration tmp_29184_pict06C.GIF_547190173.gif]