The Math.tan() function returns the tangent of a number in radians.

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A number representing an angle in radians.

Return value

The tangent of x. If x is Infinity, -Infinity, or NaN, returns NaN.

Note: Due to floating point precision, it's not possible to obtain the exact value π/2, so the result is always finite if not NaN.


Because tan() is a static method of Math, you always use it as Math.tan(), rather than as a method of a Math object you created (Math is not a constructor).


Using Math.tan()

Math.tan(-Infinity); // NaN
Math.tan(-0); // -0
Math.tan(0); // 0
Math.tan(1); // 1.5574077246549023
Math.tan(Math.PI / 4); // 0.9999999999999999 (Floating point error)
Math.tan(Infinity); // NaN

Math.tan() and π/2

It's not possible to calculate tan(π/2) exactly.

Math.tan(Math.PI / 2); // 16331239353195370
Math.tan(Math.PI / 2 + Number.EPSILON); // -6218431163823738

Using Math.tan() with a degree value

Because the Math.tan() function accepts radians, but it is often easier to work with degrees, the following function accepts a value in degrees, converts it to radians and returns the tangent.

function getTanDeg(deg) {
  const rad = (deg * Math.PI) / 180;
  return Math.tan(rad);


ECMAScript Language Specification
# sec-math.tan

Browser compatibility

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See also