Double Angle Trigonometric Identities

Hey everyone this is just a refresher of what learned before the break. I hope everyone had a good spring break and also I'm sorry for the late blog i forgot it was my turn !

Double Angle Identities:

Other double identities are : csc(2a)= 1/sin(2a) Sec(2a)= 1/cos(2a)

cot(2a)= 1/tan(2a) or cos(2a)/sin(2a)

These double angle identities can be used to solve for exact values for sin(2a), cos(2a), tan(2a) .. etc. They can also be used to verify if one side of the equation is equal to the other side of the equation in trigonometric identities.

ex: sin2x=2cotxsin*2x (*2 means squared)

LHS=sin2x=2sinxcosx

RHS=2cotxsin*2x=2(cosx/sinx) X (sin*2x)= 2cosxsinx

ex: 2sinπ/12cosπ/12

θ=π/12

sin2(π/12)

sin(π/6)

sin(30)

Using a special triangle: a=root3 o=1 h=2

sinx=o/h=1/2

By: robert jerao