hey all hope ur fine!!

i need ur help :

knowing that: cos (a+x) =cosa.cosx - sina.sin X show, by derivation that: sin (a+x) =sina.cos x+ cosa.sin X

anny help guys?

many thanks

Results 1 to 3 of 3

- May 16th 2007, 10:16 AM #1

- Joined
- Oct 2006
- Posts
- 78

- May 16th 2007, 10:20 AM #2

- Joined
- Nov 2005
- From
- New York City
- Posts
- 10,616
- Thanks
- 10

- May 16th 2007, 10:37 AM #3

- Joined
- May 2006
- From
- Lexington, MA (USA)
- Posts
- 12,028
- Thanks
- 847

Hello, iceman!

Knowing that: .cos(a + x) .= .cos(a)·cos(x) - sin(a)·sin(x)

show by derivation that: .sin(a + x) .= .sin(a)·cos(x) + cos(a)·sin(x)*a*is a constant.

If "by derivation" means "differentiation", the proof goes like this . . .

Differentiate the given equation:

. . . . . . . . . . .-sin(a + x) .= .cos(a)·[-sin(x)] - sin(a)·cos(x)

. . . . . . . . . . .-sin(a + x) .= .-sin(a)·cos(x) - cos(a)·sin(x)

Multiply by -1: .sin(a + x) .= .sin(a)·cos(x) + cos(a)·sin(x)