Question

In triangle ABC, what is the measure of A if a = 15, b = 10, and c = 7?
57.12°
72.15°
103.21°
122.88°

Answer 1

for this one, use the law of cosines so, a^2 = b^2 + c^2 - 2(b)(c)cosA.
for you, thats: 15^2 = 10^2 + 7^2 - 2(10)(7)cosA

Answer 2

225 = 149 - 140cosA. subtract the 149 from both sides so you have 76 = -140cosA

Answer 3

divide 76 by -140

Answer 4

the answer is not an answer choice

Answer 5

you should get a pretty long decimal that is about -0.5429

Answer 6

take the inverse cosine of that decimal

Answer 7

your answer is about 122.88 and that would be degrees

Answer 8

ohh i understand now!! thank you!!

Answer 9

sure thing