# advanced functions

posted by
**Anonymous**
.

Use the Pythagorean Identify to show that the double angle formula for cosine can be written as:

cos2x = 2cos^2x - 1

posted by
**Anonymous**
.

Use the Pythagorean Identify to show that the double angle formula for cosine can be written as:

cos2x = 2cos^2x - 1