Saturday

April 19, 2014

April 19, 2014

Posted by **donny** on Friday, April 30, 2010 at 9:08pm.

Find cos(s + t) given that cos s = 1/3, with s in quadrant 1, and sin t = -1/2, with t in quadrant 4.

- trig -
**Reiny**, Friday, April 30, 2010 at 9:20pms in I

if cos s = 1/3, then sin s = √8/3

t in IV

if sin t = -1/2, then cos t = √3/2

cos(s+t)

= cosscost - sinssint

= (1/3)(√3/2) - (√8/3)(-1/2)

=(√3 + √8)/6

- trig -
**donny**, Friday, April 30, 2010 at 9:49pmthis is the wrong answer..

- trig -
**Reiny**, Friday, April 30, 2010 at 11:02pmI am 100% sure my answer is right.

What have they got?

Is is (√3 + 2√2)/6 perhaps.

If it is, I will let you think about it.

- trig -
**donny**, Friday, April 30, 2010 at 11:27pmyes, (√3 + 2√2)/6 is the correct answer/form. thank you for your help!

**Related Questions**

Precal - I do not understand how to do this problem ((sin^3 A + cos^3 A)/(sin A...

Trig Help! - Question: Trying to find cos π/12, if cos π/6 = square ...

MATH - Hi, I really need help with these questions. I did some of them halfway, ...

TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...

Trig. Law of Cosines - Show that any triangle with standard labeling... a^2+b^2+...

trig - I'm confused with this concept: Okay, so I have this problem: cos2x( 2 ...

trig - The expression 4 sin x cos x is equivalent to which of the following? (...

trig - how would you verify this trig identity (1+cos(x) / 1-cos(x)) - (1-cos(x...

Math - Calculus - The identity below is significant because it relates 3 ...

algebra - Can someone please help me do this problem? That would be great! ...