## Math4Life Use a half–angle identity to find the exact value of sin 105° one year ago one year ago

1. ParthKohli

$\sin(90 + 15) = \sin(90)\cos(15)+\sin(15)\cos(90)$The second term would cancel.

2. ParthKohli

I would use the half-angle identity to find $$\sin(15)$$.

3. Math4Life

I'm confused, we haven't learned this yet, i'm doing extra credit where we do a practice on the next thing we learn that we haven't been taught yet to see how we do can you explain?

4. ParthKohli

Do you know what the half angle identity says?

5. Math4Life

what does it say?

6. ParthKohli

Sorry, was afk. I think it is a lot of typing so here: http://www.mathwords.com/h/half_angle_identities.htm

7. Math4Life

Trig identities that show how to find the sine, cosine, or tangent of half a given angle.

8. Math4Life

@ParthKohli You there? What's next?

9. ParthKohli

Use those to find $$\sin(15)$$ from $$\sin(30)$$.