TUTORIAL: coordinate in triangle. processing / java

checking if a set of co-ordinates are inside a circle is easy, some with a rectangle. but no easy way to check if you are in a triangle exists. but i have found a way to do it, and it's not even that complicated. in the video I explain exactly how and why it works, but the code is down here for you to copy too.
please do credit me if you use this solution, people will find out anyway. it's a minor thing to credit me for what i think is a tat of a smart solution.


(smaller then symbols aren't allowed. smaller then will be refereed to as --==. a simple find and replace will fix it)

private boolean onTriangle(float mx, float my, float ax, float ay, float bx, float by, float cx, float cy){

double ab = calculateDistance(ax, ay, bx, by);
double bc = calculateDistance(bx, by, cx, cy);
double ac = calculateDistance(ax, xy, cx, cy);

double am = calculateDistance(mx, my, ax, ay);
double bm = calculateDistance(mx, my, bx, by);
double cm = calculateDistance(mx, my, cx, cy);

double abc = calculateAngle((float)(ab),(float)(bc),(float)(ac));
double bca = calculateAngle((float)(bc),(float)(ac),(float)(ab));
double cab = calculateAngle((float)(ab),(float)(ac),(float)(bc));

double abm = calculateAngle((float)(ab),(float)(bm),(float)(am));
double bcm = calculateAngle((float)(bc),(float)(cm),(float)(bm));
double cam = calculateAngle((float)(am),(float)(ac),(float)(cm));

if(abm--===abc) {
if(bcm--===bca) {
if(cam--===cab) {
return true;
}
}
}

return false;
}

private static double calculateDistance(float x1, float y1, float x2, float y2){
return Math.pow(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2), 0.5);
}

private static double calculateAngle(float onTheSide1, float onTheSide2, float oppositeSide)/*-----DONE calculates the angle of a corner in a triangle with the length of the sides*/ {
return Math.acos((Math.pow(onTheSide1, 2) + Math.pow(onTheSide2, 2) - Math.pow(oppositeSide, 2)) / (2 * onTheSide1 * onTheSide2));
}

music:
Sedimentary by Windwolf (https://youtu.be/M8Oiajqe7Ck)
Wintersnow's Lullaby by Windwolf (https://youtu.be/d9DTvQRGp9A)
Friendship by Night Breeze(https://youtu.be/E-Gh-GtJ77Q)
The Path to the Cottage by Windwolf (https://youtu.be/RkKfBtNEC7A)
The Wolf by Windwolf (https://youtu.be/VL-psq7r1aI)
Dümelleevi by Windwolf (https://youtu.be/DttoHwAWhoA for the full song)