Question

Triangle D E F is shown. Angle D E F is 140 degrees. The length of D E is 11, the length of E F is 9, and the length of D F is e.
In ΔDEF, DE = 11, EF = 9, and angle E = 140°.



Which equation correctly uses the law of cosines to solve for the third side?

e2 = 112 + 92 − 2(11)(9)cos(140°)
112 = e2 + 92 − 2e(9)cos(140°)
92 = e2 + 112 − 2e(11)cos(140°)
e = 11 + 9 − 2(11)(9)cos(140°)

Answer 1

Answer:

e2 = 112 + 92 − 2(11)(9)cos(140°)

Answer 2

Answer:

A

Step-by-step explanation:

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