In triangle ABC, m∠A = 45°, m∠B = 40°, and a = 7. Which equation should you solve to find b?
a. b² = 7² - 2(7)bcos40°
b. 5/7 = b sin40°
c. 45° = 40° + 7b sin45°
d. 45° = 7/40 * 7b cos40°