If you're seeing this message, it means we're having trouble loading external resources on our website.

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

# Trigonometric identity example proof involving all the six ratios

Watch as we try to prove a trigonometric identity in real-time. Instead of just showing the clean and final correct path to the proof, we show how we sometimes take a few wrong turns in the path to arriving at the right path. Created by Aanand Srinivas.

## Want to join the conversation?

• After I kind of got lost.
There were too many equations
• how did he get 2sinAcscA on ? and 2cosAsecA on
• In one of the questions on the practice, it had this reasoning for the answer:

cos(38°)sec(38°)/
tan(18°)tan(35°)cot(35°)cot(18°)
=
cos(38°)tan(18°)tan(35°)/
tan(18°)tan(35°)cos(38°)
=1

How did they get from sec(38°) to tan(18°)tan(35°)? What identity was used there?
(1 vote)
• at

he changed the sin to sin^2. How is that possible?