Deriving the Law of Cosines

If three sides of a triangle are given, the Law of ____ is used to solve the triangle.

• Cosines

• Sines

• Tangent

• Cosecents

Find angle Z

• 20.15°

• 71.23°

• 51.06°

• 57.71°

Use Law of Cosines to find angle T

• 62.2°

• 53.1°

• 59.5°

• 64.7°

Find XZ

• 16.004 meters

• 544.165 meters

• 34.7 meters

• 1204.165 meters

What is the distance across the river? The two sides are 4.15 miles and 5.33 miles. The included angle measure is 37 degrees.

• 2.9 miles

• 3.2 miles

• 3.6 miles

• 3.9 miles

​ (a)   ​​ 4. Which law should I use for the given triangle?

• Law of Sines AFTER testing for #of Triangles

• Law of Sines then switch to Law of Cosines

• Law of Sines only

• None, use Right Triangle Trig

• Law of Cosines only

• Law of Cosines then switch to Law of Sines

Find QR

• 34.7 km

• 2.2 km

• 13.74

• 31.1 km

Find the missing side.

• 15.9 in.

• 22.8 in.

• 19.2 in.

• 521.1 in.

To approximate the length of a marsh, a surveyor walks 425 meters from point A to point B. Then the surveyor turns 65º and walks 300 meters to point C. Approximate the length AC of the marsh.

• 250

• 615

• :)

• Not me

Find BC

• A

• B

• C

• D