Scribe Post

Hello! This is Jaifel and it's my second scribe post. When we entered the class, Mr. K asked us to find the exact value of :

a. sin 100° cos 50°+ cos 100° sin 50°
we know that this is the sine law

sin (100° + 50°)
sin (150°)
1/2


b. cos π/3 cos π/12 + sin π/3 sin π/12

from our "dance" we know that this is the cosine law

cos (π/3- cos π/12)
and we also know that the sign changes

we then used a common denominator
cos (4π/12- π/12)

and we get (3π/12) we reduce it as cos (π/4)
which has a value of

He also asked us to prove that ...................

d. cos(π+x)= cosx
cosπ cosx+ sinπsinx
-1 cosx -(0) sinx
-cosx

PROOFS OF THE SUM AND DIFFERENCE IDENTITIES