Trig (Math) Help?

pegasasu • 25 March 2014 at 5:32 PM

(becausemyfriendswon'ttalktomesobs)

Precalc/Trig problem:

"Use the value of the trigonometric function to evaluate the indicated functions."
sin t = 4/5
sin(Pi - t)
sin(t + Pi)


OTL Thanks--

spiritkoi • 25 March 2014 at 5:55 PM

@pegasasu Wouldn't you get the same number but one is negative and one is positive? I don't know, I'm still in middle school. xP

trig • 25 March 2014 at 6:37 PM

t = sin^-1 (4/5)
t is in the first quadrant.

So cos(t) = 3/5

sin(pi - t) = t
So second quadrant minus something less than 90 degrees (Q1) has to be in Q2. Since sin is positive in both Q1 and Q2, it is still t.


sin(t + pi) = -t
Using same logic, t is in Q1 (less than 90). Plus 180 degrees and you're in Q3. Q3 has negative sin. Therefore, it is -t.

QED.

pegasasu • 25 March 2014 at 9:00 PM

@spiritkoi @trig

Ahh, thank you! *^* I think I get it now. (Hehe, your username is trig. How fitting.)