Thread: Derivee?:!

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

Originally Posted by iceman1

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

Hint: sin x = cos (pi/2 -x )

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)

I assume that 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)