Mathematics, 10.05.2020 10:57, quanharris2k19

A triangle has side lengths 4, 7 and 9. What is the measure of the angle across from the longest side?

92 = 42 + 72 − 2g4g7cos(A)
81 = 16 + 49 − 56cos(A)
81 = 9cos(A)
9 = cos(A)
A cannot exist!

Gabe tried to use the law of cosines to find an unknown angle measure in a triangle. His work is shown. What is Gabe’s error?

a. Gabe reversed the order of the 9 and the 4.

b. Gabe squared the numbers incorrectly.

c. Gabe should not have subtracted 56 from
16 + 49.

d. Gabe incorrectly stated that cos–1(9) is not defined.

Answers: 1

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A triangle has side lengths 4, 7 and 9. What is the measure of the angle across from the longest sid...