With the curve

parameterized by

with

, and given the vector field

the work done by

on a particle moving on along

is given by the line integral

where

The integral is then


Answer:
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Step-by-step explanation:
Required
Show that:

To make the proof easier, I've added a screenshot of the triangle.
We make use of alternate angles to complete the proof.
In the attached triangle, the two angles beside
are alternate to
and 
i.e.


Using angle on a straight line theorem, we have:

Substitute values for (1) and (2)

Rewrite as:
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<em> -- proved</em>
Answer:
>
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