In Angle QRS, QR=31.9, RS=25.2, and QS=37.6. To the nearest tenth, what is the measure of angle R?
+128460 Using the Law of Cosines
QS^2 = QR^2 + RS^2 -2 ( 31.9 * 25.2) cos ( QRS)
(37.6^2 - 31.9^2 - 25.2^2) / [ -2 ( 31.9 * 25.2) ] = cos (QRS)
Taking the cosine inverse to find angle QRS we have
arccos [ (37.6^2 - 31.9^2 - 25.2^2) / [ -2 ( 31.9 * 25.2) ] ] = QRS = 81.46° = 81.5°
