Find the angle B in an oblique triangle in which a=31 b=15 and c=17?

0 ⤊

a. 13deg 28'
b. 15deg 19'
c. 148deg 47'
d. 151deg 13'

2007-04-15 05:24:49 · 2 answers · asked by simba22 1 in Science & Mathematics ➔ Mathematics

use law of cosines

cos B =(a^2 + c^2 - b^2)/2ac
=(31*31 +17*17 -15*15)/2*31*17
=(961+ 289 -225)/1054
=.9724
B =13 deg 28'

2007-04-15 05:38:44 · answer #1 · answered by bignose68 4 · 0⤊ 0⤋

15² = 17² + 31² - 2 x 17 x 31 cos B
34 x 31 cos B = 17² + 31² - 15²
cos B = 1025 / (34 x 31)
B = 13° 28`
ANSWER a

2007-04-15 06:55:58 · answer #2 · answered by Como 7 · 0⤊ 0⤋