Trigonometry dilemma -sum to product identities
Favorites|Homepage
Subscriptions | sitemap
HOME > Mathematics > Trigonometry dilemma -sum to product identities

Trigonometry dilemma -sum to product identities

[From: ] [author: ] [Date: 11-08-05] [Hit: ]
can someone plz help me with this?put a = x and b = 7x and simplify.-........
It has been a really long time since i have done anything Trig and i am having difficulty remembering. i am asked to use the sum to product identities to find an identity for cos x - cos 7 x............can someone plz help me with this?

-
cos a - cos b = -2 sin((a+b)/2) sin((a-b)/2)
put a = x and b = 7x and simplify.

-
.. cos(x) - cos(7x)
= cos(x) - [ 64cos^7(x) - 112cos^5(x) + 56cos^3(x) - 7cos(x) ]
= - 64cos^7(x) + 112cos^5(x) - 56cos^3(x) + 8cos(x)
= - cos(x) [ 64cos^6(x) - 112cos^4(x) + 56cos^2(x) - 8 ]
= - 8 cos(x) (cos(x) - 1) (cos(x) + 1) (2cos(x) - 1) (2 cos(x) + 1) (2 cos²(x) - 1)
1
keywords: product,to,Trigonometry,dilemma,identities,sum,Trigonometry dilemma -sum to product identities
New
Hot
© 2008-2010 http://www.science-mathematics.com . Program by zplan cms. Theme by wukong .