Pre-calc question again
Favorites|Homepage
Subscriptions | sitemap
HOME > > Pre-calc question again

Pre-calc question again

[From: ] [author: ] [Date: 12-06-21] [Hit: ]
sin A = sin arcsin 1/4 = 1/4 (easy right?Well,......
Dude told me to post them seperately, so...
find exact value of
cos(2 arcsin(1/4))
How can i do it?
The thing was HOW DO I DO IT WITHOUT A CALCULATOR? Hence the words, "how can I do it?"
I would like to know how to do it without a calculator, considering I will have to do problems like it on the final tomorrow. So stop saying to use a calculator! Please, if you're going to say for me to use a calculator, then please do not answer!

-
cos(2 arcsin(1/4))

Replace: arcsin(1/4) = A

Cos 2A = (cos A)^2 - (sin A)^2

sin A = sin arcsin 1/4 = 1/4 (easy right?)

(cos A)^2 = 1 - (sin A)^2 = 1 - (sin arcsin 1/4)^2 = 1 - (1/4)^2 = 1 - 1/16 = 15/16

Cos 2A = (cos A)^2 - (sin A)^2 = 15/16 - (1/4)^2 = 15/16 - 1/16 = 14/16 = 7/8

cos(2 arcsin(1/4)) = 7/8

Well, you still need a calculator to calculate 7/8 :)))
1
keywords: Pre,again,question,calc,Pre-calc question again
New
Hot
© 2008-2010 http://www.science-mathematics.com . Program by zplan cms. Theme by wukong .