Answer:
15)
2cos(300) = 1
2cos(-45) = 1.41
2cos(0) = 2
17)
(2) 90
18)
sin2(180) + cos(180) = 1
Step-by-step explanation:
You have to know about the unit circle to do this one.
Because the radius is 1, we can directly measure sine, cosine and tangent.
It's something you have to memorize.
What happens when θ is 90°?
cos 90° = 0, sin 90° = 1 and tan 90° is undefined
What happens when the angle, θ, is 0°?
cos 0° = 1, sin 0° = 0 and tan 0° = 0
