I have some work and im confused on these problems... I did all i can (looked in book and such) and need help.
Simplify the expression cos (X-5pie /2)
For this one i know that you can go to (cosx)(cos-5pie/2) + (sinx)(sin-5pie/2) But i dont know what to do from there
second is If cotx= 4/3 and 180degrees< x < 270degrees, find the exact values of sin2x and cos2x
Here, i know if there was a triangle, there would be the 5,4,and3 to it, but i dont know how you go to the sin2x and cos2x
third is Find the solutions of sin2x = cosx that are in interval [0, 2pie)
If anyone could help, youd be my hero. I have 8 tests this week and im stressing out on these problems....
Dec 19th 2006, 07:52 PM
1) Simplify: .
What you did was almost correct . . .
Note that is equivalent to . . so we have: .
. . . . . . . . . .
2) If and degrees,
find the exact values of and
First, note that is in Quadrant 3.
Since , we have: . . . Then: .
Using double-angle identities, we have:
3) Find the solutions of: . in the interval
And we have two equations to solve:
. . . .
Dec 20th 2006, 04:31 PM
Ty again for your help. However just one thing that I found as these were graded. For the first problem it was +sinx .. not -sinx :p