Posted by Natalie on .
Prove or disprove the following identity:
cos (x+pi/6) +sin (xpi/3) = 0

Precalculus with Trigonometry 
Reiny,
I will use 30° and 60° , easier to type
cos (x+300) +sin (x60)
= cosxcos30  sinxsin30 + sinxcos60  cosxsin60
= (√3/2)cosx  (1/2)sinx + (1/2)sinx  (√3/2)cosx
= 0
= RS