Law of Cosines

Question 1

In ΔDEF, DE = 11, EF = 9, and angle E = 140°. Which equation correctly uses the law of cosines to solve for the third side?

Revolt · Accepted Answer

A: e2 = 112 + 92 − 2(11)(9)cos(140°)

Question 2

Which of these triangles can you use the law of cosines to solve for a missing side?

Revolt · Accepted Answer

B: [Image: A triangle has side lengths x, 8, and 12. The angl...]

Question 3

A surveyor measures the lengths of the sides of a triangular plot of land. What is the measure of the angle of the triangular plot at which the surveyor stands? Approximate to the nearest degree.

Revolt · Accepted Answer

B: cos–1(0.125) = 83°

Question 4

What is true when the plane is 100 meters away from takeoff? Check all that apply.

Revolt · Accepted Answer

B: The given information is the SAS case.; D: Evelyn is approximately 104 meters from the plane.; E: The angle of elevation of the plane is 12°.

Question 5

A pilot flies 720 miles from Dallas, Texas, to his first destination. After dropping off his cargo, he flies southeast 290 miles to his second destination. If the angle formed by his trip is 125°, what is the distance he will fly from the second destination back to Dallas?

Revolt · Accepted Answer

B: 918 miles

Question 6

ΔDEF is an isosceles triangle with base angles E and F.

Revolt · Accepted Answer

: 14; : 83

Question 7

ΔDEF is an isosceles triangle with base angles E and F.

Revolt · Accepted Answer

: 113569; : 83

Question 8

Question 8

Revolt · Accepted Answer

83

Question 9

Question 9

Revolt · Accepted Answer

113571

Law of Cosines Answers

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