Find Inverse Tangent?

Question

I'm new to Javascript and I'm trying to use inverse tangent to find the angle in degrees between a line and the x axis on an elevated y. I don't see any command for it so I really need some help.

Phosphaturia

Do you mean arctanget? – Chaumont

Answer 1

Use Math.atan() function and then Math.toDegrees() multiply it by 180/Math.PI to convert radians to degrees Found the answer it here

Later edit:

Here is an example of angle calculation between a line defined by 2 points (A and B) and the X axis. The elevation of the second line (parallel with the X axis) is irrelevant since the angle stays the same.

 /*
 * Calculates the angle between AB and the X axis
 * A and B are points (ax,ay) and (bx,by)
 */
function getAngleDeg(ax,ay,bx,by) {
  var angleRad = Math.atan((ay-by)/(ax-bx));
  var angleDeg = angleRad * 180 / Math.PI;
  
  return(angleDeg);
}

console.log(getAngleDeg(0,1,0,0));

Merman

what do I put into the atan? is it all 3 x's and y's – Phosphaturia

If a ratio is being used, it is better to use Math.atan2(y, x). It gets the correct quadrant and avoids possible division by zero problems. – Blackman

@AndrewMorton I don't see how atan2() would avoid the division by zero edge case this needs to be checked first to see if ax and bx are identical and then to see if the two points A and B are identical – Merman

@Merman The function does the check itself, and works correctly for all four quadrants: Math.atan2 documentation. – Blackman

Answer 2

I found this short and simple:

const calculateAngle = (width, height) => Math.atan(width/height)/(Math.PI / 180) // Angle in degrees

Posen

Answer 3

Try using Math.atan (outputs angle in radians) and some trigonometry.

Til

Answer 4

Questions like these are best answered by the reference. I see a bunch of trigonometric functions there, including:

• acos()
• asin()
• atan()
• atan2()
• cos()
• degrees()
• radians()
• sin()
• tan()

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