What is the right choice for question 2) ?

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We are asked to find the slope of the secant line between `x=pi/2` and `x=(5pi)/8` for the function `y=-cos(x-pi/4)` .

The slope of the secant line between points `(a,f(a)),(b,f(b))` is

`m=(f(b)-f(a))/(b-a)` .

`y_((5pi)/8)=-cos((5pi)/8-pi/4)=-cos((3pi)/8)~~-.383`

`y_(pi/2)=-cos(pi/2-pi/4)=-cos(pi/4)=-sqrt(2)/2~~-.707`

The slope is `m~~(-.383-(-.707))/((5pi)/8-pi/2)~~.324/(pi/8)~~.826`

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The answer is (b)

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