Find the angle b in an oblique triangle in which a = 31, b = 15, and c = 17. a. 13º28' b. 15º19' c. 151º13' d. 148º47'

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We can find the measure of angle B using the Law of cosines.

According to the Law of Cosines:



Using the values of a,b and c in the above equation we get:



Thus measure of angle B is 13.47 degrees. We can convert the decimal part to minutes by multiplying it by 60.

So measure of angle B will be 13 degrees and (60 x 0.47) minutes which equals 13 degrees and 28 minutes or 13° 28'.

Thus option A gives the correct answer.