Cos 2 Theta Calculator

Your details

Choose whether to start from a raw angle or from known trig values of theta.
Unit of the angle theta.
The angle theta. Result will be cos(2 * theta).
deg
cos(2theta)Positive
0.5

The cosine of the double angle

Form 1: cos^2(t) - sin^2(t)0.5
Form 2: 2cos^2(t) - 10.5
Form 3: 1 - 2sin^2(t)0.5
sin(theta)0.5
cos(theta)0.866025
Angle (degrees)30deg
0.5
Strongly negative<-0.5Negative-0.5-0Positive0-0.5Strongly positive0.5+

For theta = 30.00 deg, cos(2theta) = 0.500000.

  • cos(2theta) = 0.500000, which means the double angle (2theta = 60.00 deg) has a cosine of 0.5000.
  • All three double-angle identities give the same value: form 1 = 0.500000, form 2 = 0.500000, form 3 = 0.500000.

Next stepTo find cos(4theta), apply the identity again with 2theta as your new input angle.

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