Given ABC with a = 23, b = 17, and c = 19, find mA . Round the cosine value to the nearest thousandth and answer to the nearest hundredth.

Answer 1

A simple application of the cosine law:
23^2 = 17^2 + 19^2 - 2(17)(19)cosA
solve for cosA, set your calculator to degrees, press 2nd F cos
(I anticipate an obtuse angle, since cosA will be negative.)

let me know what you get

Answer 2

I got 4

Answer 3

You are looking for the size of the angle.
You got 4 ?????

from:
23^2 = 17^2 + 19^2 - 2(17)(19)cosA
529 = 289+361 - 646cosA
646cosA = 121
cosA = 121/646
angle A = appr 79.20° to the nearest hundredth

I was wrong to guess that the cosine would turn out negative