Question

Linear Approximation help!
I need a step-by-step guidance.

Let f(x)=sin(x/2).If x=1 and dx=1/2, what is dy?

Answer 1

what I did so far:
dy/dx = f'(x)

so dy = f'(x) dx
dy = 1/2 cos (x/2) dx

sub in values:
dy = 1/2 cos (1/2) x (1/2)
dy is approx 0.25

but the book says 0.22, how to get exactly 0.22?

Answer 2

@zepdrix @Directrix @dan815

Answer 3

what is this ".Ifx=1 "

Answer 4

there should be a space , sorry

"If x=1 and dx=1/2, what is dy? "

Answer 5

http://prntscr.com/8zjg0f

Answer 6

cos(1/2)=~0.88
1/4*(cos(1/2))=~0.22

Answer 7

yeah, i was gonna say use radians instead of degrees

Answer 8

oh I see, so my solution is right?
I only have to change it to radians...

thank you ! :)

Answer 9

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