Current time:0:00Total duration:6:02

0 energy points

# Proof of the cosine angle addition identity

Sal proves the identity cos(x+y) = cos(x)*cos(y) - sin(x)*sin(y). Created by Sal Khan.

If you're seeing this message, it means we're having trouble loading external resources for Khan Academy.

If you're behind a web filter, please make sure that the domains ***.kastatic.org** and ***.kasandbox.org** are unblocked.

Main content
# Proof of the cosine angle addition identity

Current time:0:00Total duration:6:02

0 energy points

Sal proves the identity cos(x+y) = cos(x)*cos(y) - sin(x)*sin(y). Created by Sal Khan.