# Math Help - Exact Value of trionometric ratio

1. ## Exact Value of trionometric ratio

How do i find the exact values without using a calculator? I'll use calculator to check..but how do i do it without...

$tan 5/4 \pi$
and
$sin330^o$

i need help on both please.

2. sin 330:

Use the trigonometric identity, sin(360-x) = - sin x
I can re-write 330 as 360 - 30
So, sin(360-30) = - sin 30 which is one of the basic ratios to find out.

tan 5pi/4 = tan (pi+ pi/4)
Use the identity: tan (pi+ x) = tan x
so, tan (pi+ pi/4) = tan pi/4.

That solves the problem.
Hope it helped,
MAX

3. Originally Posted by crosser43
How do i find the exact values without using a calculator? I'll use calculator to check..but how do i do it without...

$tan 5/4 \pi$
and
$sin330^o$

i need help on both please.
you need to learn the unit circle ...