In this video you are shown the Pythagorean identities and how they are derived. In a later tutorial you will have to prove identities using these.

Pythagorean Identities:

  •     \[{{{\sin }^2}\theta  + {{\cos }^2}\theta  \equiv 1}\]

  •     \[{1 + {{\tan }^2}\theta  \equiv {{\sec }^2}\theta }\]

  •     \[{1 + {{\cot }^2}\theta  \equiv {\rm{cose}}{{\rm{c}}^2}\theta }\]