Finding Slope with Desmos and Table

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karush
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Printed exercise 4: The point P(0.5, 0) lies on the curve y = cos πx. Part (a) asks for the slope of secant line PQ, Q = (x, cos πx), for x = 0, 0.4, 0.49, 0.499, 0.51, 1, 0.6, 0.501.

ok attemped to do this desmos but was sondering if there is away to get these slope in a 3rd column in the table with $m=\dfrac{\delta y}{\delta x}$

Screenshot of a Desmos graph of a decreasing cosine-like curve from (0, 1) to (1, -1), with a table of x and y values beside it and points plotted near x = 0.4, 0.49, 0.5, 0.51 and 0.6.
 
I just thot it would be cute if I did,,
 
How is the derivative relevant at all? The problem does not ask for the slope of the tangent line, it asks for the slope of the "secant" line, through P= (0.5, 0) and $Q= (x, cos(\pi x))$ for various values of x.

For (i) x= 0 so Q= (0, 1) and the slope of the slope of the secant line is $\frac{0- 1}{0.5- 0}= -2$. For (ii) x= 0.4 so Q=(0.4, 0.9998) so the slope of the secant line is $\frac{0- 0.9998}{.5- .4}= -9.998$ (to three decimal places).

What do you get for the others?