Question

how do I use the half-angle formula to determine the exact value of the given trigonometric expression? cot(3pi/8)

Answer 1

Assumming you only have half-angle formula for sin and cos.
What is cot(x) in terms of cos(x) and sin(x)?

Answer 2

cosx/sinx

Answer 3

What are the half angle formulae for those sin and cos?

Answer 4

\[\cos(x/2)=\sqrt{(1+cosx)/2} , \sin(x/2)= \sqrt{(1-cosx)/2} \]

Answer 5

the half-angle formula for sin, cos, and tan u can look here :
http://www.freemathhelp.com/trig-double-angles.html
also, (3pi/8) if u converting to degrees it can be 135/2 degrees