## How do I plot the angle

Umut Ayyildiz

### Umut Ayyildiz (view profile)

さんによって質問されました 2019 年 1 月 29 日

### Brian Hart (view profile)

さんによって 回答されました 2019 年 1 月 30 日
Brian Hart

### Brian Hart (view profile)

さんの 回答が採用されました
A boat moves at 20kmh^−1 along a straight path described by
y =11x/15+43/3
starting at x = −10; y = 7. Plot the angle (in degrees) of the line of sight from an observer at the coordinate origin to the boat as a function of time for 3 hours.
This is what I have so far
x=-10:20:50
y=((11*x)/15)+(43/3)
plot(x,y)
hold on
a=atand(y/x)
legend('boat')

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## 1 件の回答

### Brian Hart (view profile)

2019 年 1 月 30 日
採用された回答

Hi Umut,
This is a neat problem! Some nice physics with rectangular-to-polar conversions and trig asymptotes. My code to solve the problem is below. There's a fair amount of background knowledge needed to understand the math.
%define constants
vel = 20 / 60; %km/min
slope = 11/15;
yInt = 43/3;
xStart = -10;
yStart = 7;
tMax = 3*60; %max time in minutes
tInc = 5; %compute for five minute increments
%Make a vector of time values for which to compute x, y position:
tVec = 0:tInc:tMax;
%Compute the radial distance from the starting point at each time interval:
distArr = tVec * vel;
% Compute the x, y position at each time interval:
xArr = xStart + cos(lineAngle) * distArr;
yArr = yStart + sin(lineAngle) * distArr;
figure;plot(xArr,yArr,'x');title('Boat position at each time interval')  