posted by Gregory .
RST is a triangle with right angle S. If s- 21.3 Angstroms and t=8.71 Angstroms, find the measure of the larger acute angle.
t + r > s,
8.71 + r > 21.3,
r > 21.3 - 8.71,
r > 12.6.
Therefore, R is the larger acute angle.
cosR = t/s = 8.7 / 21.3 = 0.40845,
R = 65.9 Deg.