Quiz Solution for Math 1321 - Quiz 3 - Problem 1 and 2, Quizzes of Trigonometry

Download Quiz Solution for Math 1321 - Quiz 3 - Problem 1 and 2 and more Quizzes Trigonometry in PDF only on Docsity! Math 1321 Quiz 3 Name: September 11, 2002 Instructions: 1. Be sure to show all your work, NO WORK = NO CREDIT!! 2. Read all questions carefully and be sure to give the result wanted. 3. Box in or highlight your final answer. NO BOX = NO CREDIT 1. Exercise 1.7, Problem 8: Compute the exact value of the following expression. DO NOT USE A CALCULATOR. 3 cos4 30o − 5 sin3 30o − sin2 45o − sin 90o Solution: 3 cos4 30o − 5 sin3 30o − sin2 45o − sin 90o =3(cos 30o)4 − 5(sin 30o)3 − (sin 45o)2 − (sin 90o) =3 (√ 3 2 )4 − 5 ( 1 2 )3 − (√ 2 2 )2 − (1) =3 ( 9 16 ) − 5 ( 1 8 ) − ( 1 2 ) − (1) = ( 27 16 ) − ( 10 16 ) − ( 8 16 ) − ( 16 16 ) =− 7 16 2. Identify as true or false and GIVE REASONS. DO NOT USE A CALCULATOR. cos 30o + cos 60o = cos 90o Solution: Well cos 30o = √ 3 2 and cos 60o = 1 2 so cos 30o + cos 60o = √ 3 2 + 1 2 6= 0 = cos 90o 1