silverfox12
New member
- Joined
- Apr 2, 2015
- Messages
- 6
Please help!! From this formula :[ sin(x+h) - sin (x) ] / h
how do i get this : [ 2 sin h/2 cos (x + h/2) ] / h ???
how do i get this : [ 2 sin h/2 cos (x + h/2) ] / h ???
Please help!! From this formula :[ sin(x+h) - sin (x) ] / h
how do i get this : [ 2 sin (h/2) cos (x + h/2) ] / h ???
I might actually need more help here . As you've said sin(a+b) = sin(a)*cos(b) + cos(a)*sin(b)
Using that : sin(x + h/2) - sin(x - h/2) = [sin(x)*cos(h/2) + cos(x)*sin(h/2)] - [sin(x)*cos(h/2) - cos(x)*sin(h/2)] if got it right . But after some work (namely just adding and subtracting) i get something like this cos(x)*sin(h/2) + cos(x)* sin(h/2)which i think equals 2*sin(h/2)*cos(x) the problem is that according to the textbook it should be like this 2*sin(h/2)* cos(x + h/2) could you please help with this too ? Any idea ?
The last question i swear .
I understand this
sin(a+b) - sin(a-b ) = 2cos(a)sin(b)
But how do i determine what should i insert instead of A and B ?
Like in this particular example sin(x + h) - sin( x) . You chose A = x + h/2 and B = h/2 but why ?
sin(x + h/2) - sin(x - h/2)
sin(A + B ) - sin(A - B ) here shouldn't A be equal to x and B equal to h/2 given these formulas ??
I'm getting something wrong just cant find out what exactly . But why do i chose A as the whole(x + h/2) and B only as the h/2 part of (x - h/2); What's the rule of choosing A and B ?