Reading Assignment
There are 2 important identities that you should be aware of. We will not use them all that much in this class as
they are more useful in a Geometry centered Trig course whereas this is more of a functional Trig course. In any
case it is good to be aware of these identities especially if you have never seen them before. If necessary I will give
you these identities on an exam so you need not memorize them. You can watch the proofs of these identities at
this link, and I encourage you to just that. As a warning this guy is a bit slow for me so I suggest watching him at
1.5X speed or even 2X.
https://www.khanacademy.org/math/trigonometry/less-basic-trigonometry/law-sines-cosines/v/law-of-cosines
• Given any triangle with sides a, b, c and angles α opposite a, β opposite b, and θ opposite c as depicted below we
have that
Law of Cosines:
a2 = b2 + c2 − 2bc cos(α)
Law of Sines:
a
b
c
=
=
sin(α)
sin(β)
sin(θ)
1