Answer:
m∠4= 360-(m∠A+m∠1+m∠3+m∠C+m∠2)
Step-by-step explanation:
In the diagram. check attach image
m∠A + m∠B + m∠C + m∠D = 360º.
Every quadrilateral can be decomposed (cut apart) into two triangles, each of whose angles' measures sum to 180º.
m∠A + m∠1 + m∠ 3 = 180º
m∠C + m∠2 + m∠4 = 180º
m∠A+m∠1+m∠3+m∠C+m∠2+m∠4 = 360º
therefore :
m∠4= 360-(m∠A+m∠1+m∠3+m∠C+m∠2)
