Question

Find the measure of

Answer 1

∠ ABC ≈ 137.9°

Explanation:

Using the Cosine rule in Δ ABC

cos B =
`(a^2+c^2-b^2)/(2ac)`

with a = 89, b = 144, c = 65

cos B =
`(89^2+65^2-144^2)/(2(89)(65))` =
`(7921+4225-20736)/(11570)` =
`(-8590)/(11570)` , thus

B =
`cos^(-1)` ( -
`(8590)/(11570)` ) ≈ 137.9° ( to the nearest tenth )