Evaluate this:

Question

Evaluate: cos 5pi/4 + cos (-pi/6)

Answer 1

Use your unit circle to find the values of cos ^5π/₄ and cos(-^π/₆)

 

cos ^5π/₄ = -^√2/₂

 

cos (-^π/₆) = ^√3/₂

 

Add them together and you get ^{(√3 - √2)}/₂