Answer:
Those are trigonometric identities. and tan is just a shortened version of tangent, same for cos is means cosine
The sine/sin of the angle = the length of the opposite side divided by the length of the hypotenuse.
The cosine/cos of the angle = the length of the adjacent side divided by the length of the hypotenuse.
The tangent/tan of the angle = the length of the opposite side divided by the length of the adjacent side.
