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**Proving slope "m" of a secant connecting two points of the sine curve**

## Homework Statement

Write and expression for the slope m of the secant connecting the points Po(Xo,Yo) and P(X,Y) of the sine curve. Use the appropriate trigonometric identity to show that m= sin((X-Xo)/2)/((X-Xo)/2) * cos ((X+Xo)/2)

## Homework Equations

Could somebody give a hint how to do the second proof? m= sin((X-Xo)/2)/((X-Xo)/2) * cos ((X+Xo)/2)

Basically what i need to prove is that:

(Sin(Xo)-Sin(X)) / Xo-X

**=**sin((X-Xo)/2)/((X-Xo)/2) * cos ((X+Xo)/2)

## The Attempt at a Solution

I could manage to do the first part of the exercise, as far as now I got a formula which is the following:

m= (Yo-Y)/(Xo-x) = (Sin(Xo)-Sin(X)) / Xo-X

and the expression (Sin(Xo)-Sin(X)) / Xo-X is equal to m