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# calculate angles

edited April 2014

Hi, i have the following question: i have a triangle with a 90° angle and want to calculate Alpha. How can I do this? Please help me

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• I diagram would be helpful, not sure what alpha in the context of a right triangle

• i found this too, but i want to calculate an angle, what they don't do in this tutorial...

• Depends what you have: how many sides and angles you know.....

• edited April 2014

If you have 3 angles (which I'm guessing you don't) you do CosX=a^2+b^2-2abCosC. If you have at least an angle and a side and 2 others, if you post them and I'll tell you what to do (it's a bit complicated to explain). :) Hope I can help

• If a diagram is not a comfortable method to explain a problem, you could explain it taking some other example or in simple words.

This link shows the basic needs you might need to fulfill http://processing.org/tutorials/trig/

Weave and Connect

• oh yes. i see. sorry.

but checkout this chapter of the the nature of code book: http://natureofcode.com/book/chapter-3-oscillation/

especially chapter 3.4

• In my opinion this question is not solved in the tutorial

here...

``````int angle;

int centerX=200;
int centerY=200;

void setup() {
size(700, 700);
background(110);
}

void draw() {
background(110, 11);

float angle2 =   atan2(moveY2, moveX2);

angle2 = map (angle2-HALF_PI, -PI, PI,
0, TWO_PI);

// white point
stroke(255);
fill(255, 2, 2);
point(moveX, moveY);

// 2 green lines
stroke(0, 111, 0);
line (moveX, centerY, centerX, centerY);
line (centerX, centerY, centerX, moveY);

// display text : angle
fill(110);
noStroke();
rect (width-200, height-200, 200, 200);
fill(0);
stroke(0);
text ("angle: "
+ angle + "\n"
+ moveX+","
+ moveY, width-100, height-100);

print(angle +", ");
float result=degrees(angle2)+0;
if (result<0)
result=result+360;
int result2 = int (round(result));
if (result2!=  angle)
print ("wrong: ");

println(result2);

// increase
angle++;
}
``````
• edited April 2014

my solution uses opposite side and adjacent side (between those is the right angle) to calculate the angle named θ

see the tutorial, 1st image, for these namings I use

http://processing.org/tutorials/trig/

• my solution is not short nor elegant...