Question 1110589: If sin(A)=-5/13. Find:
1. cos(2A)
2. sin(2A)
2. Cos(4A)
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! If sin(A)=-5/13. Find:
1. cos(2A)
2. sin(2A)
2. Cos(4A)
--------------------
Step 1, find cos(A)
cos(A) = sqrt(1 - sin^2) = 12/13 or -12/13
The sine is negative in Q3 and Q4. The cosine is negative in Q3 and + in Q4, so the sign and quadrant cannot be determined.
-----
sin(2A) = 2sin(A)*cos(A)
---
cos(2A) = sqrt(1 - sin^2(2A))
---
cos(4A) = cos^2(2A) - sin^2(2A)
|
|
|
