Double angle formula calculator

To find the value of sin2x, cos2x, or tan2x, put the angle in the double angle formula calculator.  


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The double angle identity calculator finds the value of a double angle for any trigonometric function if the value of an angel is provided. This calculator can compute values of:

  • Sin2x
  • Cos2x
  • Tan2x

What is a double angle?

Double angle, as the words imply, means to increase the size of the angle to twice its size. It simply means two times of a trigonometric angle i.e 2x in terms of x. 

Double angle identities are used to simplify trigonometric calculations. 

Double angle formula

The main formulas used to find a double angle are:

  • Sin2x = 2 (sinx).(cosx)
  • Cos2x= 2.cos2x -1
  • tan2x = (2.tanx)/(1 - tan2x) 

You can also calculate half angle of trigonometric identities by using our half angle identity calculator.

How to find a double angle?

You can learn to find the double angle through an example.


What is the double angle for sin 40°?


Step 1: Write the formula of sin2x.

Sin2x = 2 (sinx).(cosx)

Step 2: Put the value of the angle into the formula.

Sin2x = 2 (sin 40).(cos 40)

= 2 (0.642)(0.766)

= 0.9836