# Geometry Problem 1529: Unlock the Mystery of Triangles: Solving for the Missing Angle with 100-50-30 Degree Angles and Cevian Lengths - A High School Challenge

In a triangle ABC, angle A measures 30 degrees, angle C measures 100 degrees. BD is an interior cevian such that BD is equal to AC. Calculate the measure of angle BDC.

### Thematic Poem: Unraveling the Secrets of a Mysterious Triangle

Amidst the angles sharp and bold,
A triangle with secrets untold,
Degrees of 100, 50, and 30,
A riddle waiting to ensue.

But as we search, we may discover,
A shape with sides so equal in measure,
An equilateral, hidden within,
A hint to the mystery therein.

And as we ponder, with our minds so bright,
An auxiliary line may come in sight,
A tool to unlock the triangle's hold,
And reveal its secrets, pure as gold.

And lo and behold, what do we see?
An isosceles triangle, waiting to be set free,
With sides and angles that match so fine,
A missing angle, no longer left behind.

So let us solve this puzzle, with grace and wit,
And uncover the mysteries, bit by bit,
With equilateral, auxiliary, and isosceles,
Our journey ends in triumph, oh so seamless.

If you're interested in finding more poems with a focus on geometry, you may enjoy this collection: More geometry thematic poems.