asked 163k views
3 votes
If triangle ABC ,PMB ,MCQ are equilateral triangle prove that PMQA is a parallelogram. ​

If triangle ABC ,PMB ,MCQ are equilateral triangle prove that PMQA is a parallelogram-example-1

1 Answer

4 votes

Answer:

AQ║PM and AP║QM, hence PAQM is a parallelogram

Explanation:

You want to show PAQM in the attached diagram is a parallelogram.

Circumcircle

Consider the circumcircle of ∆ABC. Equilateral triangle ABC divides the circle into three congruent arcs, each of which is 120°.

Angle CMQ is an interior angle of equilateral triangle MCQ, so is 60°. That makes angle QMP its supplement, or 120°. Vertical angle BMC is also 120°, the measure of arc BC. This means M is the center of the circumcircle.

Since MC is congruent to MQ in equilateral ∆MCQ, point Q lies on the circumcircle. Angle AQB is thus an inscribed angle that intercepts 120° arc AB, so its measure is 60°.

Angles AQM and QMP are supplementary, which requires AQ║PM. By symmetry, AP║QM, so PAQM is a parallelogram.

If triangle ABC ,PMB ,MCQ are equilateral triangle prove that PMQA is a parallelogram-example-1
answered
User LouisK
by
8.4k points
Welcome to Qamnty — a place to ask, share, and grow together. Join our community and get real answers from real people.