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Big Ideas Math Integrated I, 2016

BI

Big Ideas Math Integrated I, 2016 View details

4. Proofs with Perpendicular Lines

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Exercise 28 Page 526

How many right angles are formed by two perpendicular lines?

8 angles, see solution.

Practice makes perfect

In Euclidean geometry, whenever two perpendicular lines meet, there are 4 right angles formed.

However, in spherical geometry, a line is a circle on the sphere whose diameter is equal to the diameter of the sphere. Therefore, lines in spherical geometry will meet twice — once at the front and another time at the back of the sphere.

In spherical geometry we have a total of 8 right angles formed by two perpendicular lines.

Subchapter links

Communicate Your Answer p.519

Monitoring Progress p.520-523

Exercises p.524-526