 |
| ||
| |||
|
| Math Central | Quandaries & Queries |
|
Question from shanaia, a student: given that sin A=4/5 and A is obtuse. find sin (A/2) |
Hi Shanaia,
Use the fact that $\sin^2 A + \cos^2 A = 1$ to find $\cos A.$ How do you know which sign to use?
Now use the fact that $\cos 2B = \cos^2 B - \sin^2 B = 1 - 2 \sin^2 B$ with $ B = \large \frac{A}{2}.$
Penny
| ||
| ||
| ||
 |
 |
|
Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.