How to use this cosine calculator
- Type an angle into the main field — a plain number such as 60, an expression such as 2+1, or a multiple of π such as 2π (the π button inserts the symbol).
- Pick the unit next to the field: ° for degrees (60° gives cos = 0.5) or rad for radians (2π rad gives cos = 1).
- Press Calculate. The result is cos(x) rounded to 8 decimal places, exactly the way the classic cos(x) calculator pages compute it.
- For unit-tagged expressions, use the cosine expression box: type cos(60 deg) or cos(2 rad) and press Calculate.
- To go backwards, enter a cosine value between -1 and 1 in the inverse cosine calculator to get arccos — both solution families, e.g. 60°+360k and -60°+360k (k = ...,-2,-1,0,1,2,...).
The cosine of an angle is the x-coordinate of the corresponding point on the unit circle, so cos(x) always lands between -1 and 1: cos(0°) = 1, cos(90°) = 0, cos(180°) = -1. The cosine curve repeats every 360° (2π radians), which is why the inverse calculator returns two solution families for every input strictly between -1 and 1. Degrees and radians convert by the usual factor — an angle in degrees is multiplied by π/180 before the cosine is taken.
Every calculation runs locally in your browser — nothing is uploaded, and no account or connection is involved. More math tools are in Math & Statistics.