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Big Ideas Math Geometry, 2014

BI

Big Ideas Math Geometry, 2014 View details

6. Solving Right Triangles

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Exercise 3 Page 505

The cosine of an acute angle in a right triangle is the ratio of its adjacent leg to the hypotenuse.

∠ C

Practice makes perfect

We want to determine which of the two acute angles in the given diagram has a cosine of 45.

The cosine of an acute angle in a right triangle is the ratio of its adjacent leg to the hypotenuse. Let's calculate cos A and sin C.

cos =adjacent/hypotenuse
cos A=AB/AC	cos C=BC/AC
cos A=3/5	cos C=4/5

We can conclude that the acute angle that has a cosine of 45 is ∠ C.

Subchapter links

Communicate Your Answer p.501

Monitoring Progress p.502-504