What is angle A and how do I get there?

Question

asked Apr 18, 2024 122k views

1 Answer

Yhenon · Answer 1 · 2024-04-24T18:53:11+0000

Work Shown:

We can use the law of cosines to determine angle A.

a^2 = b^2+c^2-2*b*c*cos(A)

27^2 = 19^2+23^2-2*19*23*cos(A)

729 = 890-874*cos(A)

729-890 = -874*cos(A)

-161 = -874*cos(A)

cos(A) = -161/(-874)

cos(A) = 0.18421053

A = arccos(0.18421053)

A = 79.38489193

A = 79.38

Your calculator needs to be in degrees mode.

The notation "arccos" refers to arccosine. It is the same as inverse cosine, aka
$\cos^(-1)$

A tool like GeoGebra can be used to confirm the answer is correct.