00:01
We are given with this figure assume this as a restaurant.
00:07
Let's consider this length as x, which makes this length as 14 minus x.
00:16
So the distance between the nearest point on the shoreline and the point where she lands is x miles.
00:25
And so this will be the distance between the point where she lands and the restaurant will be equal to 14 minus.
00:33
X miles.
00:34
So we are given that the speed of the girl while walking is three miles per hour and while drawing the board her speed is two miles per hour.
00:49
In the first part of the problem we are as to find an expression that gives the time it takes for her to reach the restaurant.
01:00
How are we going to do that? let's assume the required function as capital t.
01:05
And here observe that we have a right angle triangle so if we assume this length as d we can say d is equal to root of 2 square plus x square from the thracurant theorem so it will be equal to root of 4 plus x square so the required function t will be equal to root of 4 plus x squared by 2 plus 14 minus x divided by 3 r so this is the answer for the first part of the problem.
01:44
In the second part of the problem we are asked to find when this function reaches minimum value.
01:51
Understand that t reaches minimum when dt divided by d x is equal to 0.
01:58
So we need to find the value of derivative of the function t.
02:02
Let's do that.
02:03
T dash which is equal to dt divided by d x will be equal to differentiating capital t.
02:10
With respect to x.
02:11
So we will get 2x divided by root of 4 plus x square times 4 minus 1 by 3.
02:22
If we equate this expression to 0, we will get 3x is equal to 2 times root of 4 plus x square.
02:33
And this implies that the value of x is approximately equal to 1 .7 -888 .8 .8.
02:40
Miles.
02:43
So, when x is approximately equal to 1 .7 -385 miles, the function t reaches minimum value...