Question

Give the exact value of each of the following: 2 cos π/6

Answer 1

pi/6 is a common angle on the unit circle.... get the value for cos(pi/6) then multiply by 2...

Answer 2

If you don't want to memorize values for pi/3 and pi/6, take an equilateral triangle with unit sides and draw an altitude that divides it in half. The small angle of the two identical triangles is pi/6 or 30 degrees.. The sine should be obvious. The cosine can be obtained with Pythagoras' help.