ALGEBRA 2/TRIGONOMETRY
Tuesday, June 21, 2011—1:15 to 4:15 p.m.




4 Expressed as a function of a positive acute angle, cos (−305°) is equal
to
(1) −cos 55° (3) −sin 55°
(2) cos 55° (4) sin 55°

Follow the cosine identity that the cosine of a negative number is equal to the cosine of its positive.
cos(-a) = cos(a)
Find the cos(305). Find the difference between it and the closest factor of 90 degrees that's above it. That is 360. Subtract 305 from 360 and that is 55. That means the cos(305) = cos(55)