Expert: Richard J. Raridon - 3/17/2004

Question
Hi, I am learning trig. I don't know how to do these two questions. Please explain it in full detail or make it easy to understand Thanks
1.   angle a is acute
If cosA =1/3, find cos2A and cos4A
2.   I don't know how to graph it
Y= sin 3x + 2 cos x


Answer
1. If cosA = 1/3, then A = 70.53 degrees
2A = 141.06 degrees and cos(2A) = -0.778
4A = 282.12 degrees and cos(4A) = 0.21
2. First you have to put in values of x and calculate Y.  
For example, x = 10 degrees, Y = 2.47
x = 20 degrees, Y = 2.75
x = 30 degrees, Y = 2.73