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| #2. Use a graphing utility to determine which of the given viewing
rectangles produces the most appropriate graph of the function |
Given Problem. |
| We know the plot command, so we enter: plot({sqrt(8*x-x^2), x=-10..10); | The result looks like this:
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| We should know from algebra that if we square both sides of the original
problem we get:
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We can see here that we really have the top half of a circle whose center is located at (4,0), and whose radius is 4. |
| Now we realize what we really have, and can intelligently choose our
domain:
plot({sqrt(8*x-x^2), x=-2..10); |
Now our result looks like this:
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| This still doesn't look like a semicircle. Here Maple has automatically
picked a range for us which distorts our curve. So we now pick a range
also:
plot({sqrt(8*x-x^2)}, x=-2..10, y=-6..6); |
Now our result looks like this:
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| If we want to see the other part of the circle (which is not a part of the function in the problem), then we could enter: plot({sqrt(8*x-x^2),-sqrt(8*x-x^2)}, x=-2..10, y=-6..6); | This would then be the result:
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1.4, #20. (a) Use a graph to show that the equation
has exactly three solutions.
| Two curves are equal when they coincide or intersect. Graph each of the equal functions in the problem. | |
| In Maple, this can be done by using the following
multiple plot command:
>plot([cos(x),.3*x],x=-5..2); |
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| We can clearly see that there are three intersection points | Therefore, we have shown that there are three solutions. |
1.4, #20 (b). Find an approximate value of m such that the equation has
exactly two solutions.
| Two curves are equal when they coincide or intersect. Graph each of the equal functions in the problem, trying different values for m. | |
| Using the multiple plot command in Maple, this
can be done by literally trying a number of coefficients for x and plotting
them, observing which ones get close to intersecting the "hump" of the
cosine curve in only one point. Thus, we will have 2 solutions.
>plot([cos(x),.3*x,.4*x,.34*x],x=-5..2); |
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| It also seems reasonable that this could also happen if the slope to
our line was negative. So I tried...
>plot([cos(x),-.34*x],x=-5..4); |
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| It appears that both of these values for m, namely +.34 and -.34 yield 2 solutions. |
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15, 21, 23, 25, 27, 29
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