Please choose the correct ending to complete the given sentence: Education and Communications: [header] How to prove the angle sum property of a triangle [title] Draw a line parallel to side bc of the triangle that passes through the vertex a. [step] Label the line pq. Construct this line parallel to the bottom of the triangle. [title] Write the equation angle pab + angle bac + angle caq = 180 degrees.

Ending1: [step] Use [substeps] 2 indentations; overlap two indentations. [title] Describe the angle relative to the angle to which the triangle rose. Ending2: [step] Write the equation angle pac on the bottom, a and b but that's all you need to know for a point. [title] Separate the bottom lines of the triangle. Ending3: [step] Remember, all of the angles that comprise a straight line must be equal to 180 °. Because angle pab, angle bac, and angle caq combine together to make line pq, their angles must sum to 180 °. Ending4: [step] Draw diagonal lines across the angle 4v of the triangle directly at both shapes lines. [substeps] When they intersect, make sure you do not intersect them.

Answer format: ending1/ending2/ending3/ending4