Draw to lines in your notebook line the ones below. What is true about the lines?

THEY ARE PARALLEL. MARK THEM.

Draw a transversal. A transversal is a line that intersects two other lines.

Label the intersection points A & B.

Draw another transversal that intersects B.

What angles are equal in this picture? You do not have to write this down.

Write this down.  1   5 since they are corresponding angles.

Draw another transversal that intersect point B. What is a transversal again?

Which angle is congruent to  9? Why?

Which angle is congruent to  9? Why?

 9   11 since they are corresponding angles. Write this down.

 9   11 since they are corresponding angles. Mark this in your diagram.

Are there other angles that are congruent?

 15   16 because they are vertical angles.

What does this justify or prove? NCTMNCTM

THE SUM OF THE ANGLES IN A TRIANGLE ADD TO 180 

Website regarding triangles Practice Problems: HW

Triangles in Architecture

New design for a building in London; has not been completed yet.

Hearst Tower in Manhattan, New York

Close up view of the Hearst Tower.

The inside of a dome.

Truss bridges use the triangle — a very stable shape — to distribute load forces.

Howrah Bridge spans over the Hooghly River in West Bengal, India.

The Little Belt Bridge also known as The Old Little Belt Bridge, is a truss bridge over the Little Belt strait in Denmark.

The pyramids of Giza in Cairo, Egypt

Unitarian Meeting House built by Frank Lloyd Wright in Madison, Wisconsin.