An ant is walking up a hill. at what x does he see the blade of grass.

70 Views Asked by At

've been working on this problem with Mathematica and by hand-help with either would be fantastic. The blade of grass is given by the line segment from (32,1/5) and (32,8). The 2D hill is given by f(x)=(1/16 x^2 - 2 x + 80)/(1/16 x^2 - 2 x + 20)^2

I am struggling to figure out how to set the equations so that I can solve the point on the hill line, especially because I have to qualify that the other point on the line (which slope equal to f'(x)) must intersect only between y=1/5-8 AND not interest h(x) again (which defines the hill). Any help, detailed or theoretical is much appreciated!

1

There are 1 best solutions below

8
On

Let's say the point $x$ is the point on the hill where the ant can see the top of the blade of grass. Plugging $x$ into $h(x)$ you can get the $y$ value.

Then you can set up an equation for the slope of $h(x)$ at $x$ using the derivative of $h(x)$ and an equation of the line from that point to the top of the blade of grass using $\frac{y-y}{x-x}$ as its slope. And these two slopes should be equal.

EDIT: to clarify, i think the line equation should be the line that goes through our $(x,y)$ on the hill, and the point $(32,8)$. I am imagining a big arm hinged at one end at $(32,8)$ and allowed to drop onto the hill. And from the characteristics of the $h(x)$ I think there is only one point in the domain we are interested in that will have the same slope as that line will, since it is decreasing over that domain.

enter image description here