How do you evaluate $cos (pi/6) cos (pi/3) - sin (pi/6) sin (pi/3)$ ?

Question

3358 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-03-25T12:00:51

Zero

Apply the trig identity:
cos (a + b) = cos a.cos b - sin a.sin b
$cos (pi/6)cos (pi/3) - sin (pi/3)sin (pi/6) = cos (pi/3 + pi/6) = = cos (pi/2) = 0$

How do you evaluate cos (pi/6) cos (pi/3) - sin (pi/6) sin (pi/3)cos (pi/6) cos (pi/3) - sin (pi/6) sin (pi/3)?