trig

posted by .

can someone please help me with this problem. i'm doing my review right now and i'm stuck?

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 -

    s 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 -

    this is the wrong answer..

  • trig -

    I 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 -

    yes, (√3 + 2√2)/6 is the correct answer/form. thank you for your help!

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Trig

    Given: cos u = 3/5; 0 < u < pi/2 cos v = 5/13; 3pi/2 < v < 2pi Find: sin (v + u) cos (v - u) tan (v + u) First compute or list the cosine and sine of both u and v. Then use the combination rules sin (v + u) = sin u cos …
  2. algebra

    Can someone please help me do this problem?
  3. Mathematics - Trigonometric Identities

    Let y represent theta Prove: 1 + 1/tan^2y = 1/sin^2y My Answer: LS: = 1 + 1/tan^2y = (sin^2y + cos^2y) + 1 /(sin^2y/cos^2y) = (sin^2y + cos^2y) + 1 x (cos^2y/sin^2y) = (sin^2y + cos^2y) + (sin^2y + cos^2y) (cos^2y/sin^2y) = (sin^2y …
  4. TRIG!

    Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6 x=1 - (3/4)sin^2 2x work on one side only! Responses Trig please help! - Reiny, Monday, February 23, 2009 at 4:27pm LS looks like the sum of cubes sin^6 x + cos^6 …
  5. trig

    The expression 4 sin x cos x is equivalent to which of the following?
  6. Precal

    I do not understand how to do this problem ((sin^3 A + cos^3 A)/(sin A + cos A) ) = 1 - sin A cos A note that all the trig terms are closed right after there A's example sin A cos A = sin (A) cos (A) I wrote it out like this 0 = - …
  7. Trig

    Find cos(s+t) if cos s= -1/2 and sin t= 3/5, s and t are in quadrant II. I got the answer to be -4/10 plus -3sqrt(3)/10. Is that right?
  8. MATH

    Hi, I really need help with these questions. I did some of them halfway, but then I got stuck. Would you please help me?
  9. Pre-calculus help

    I have two problems I am stuck on, if you could show me how to solve the problems it would be much appreciated. 1) Find sin 2x, cos 2x, and tan 2x from the given information. tan x = − 1/6, cos x > 0 sin 2x = cos 2x = tan …
  10. Trig

    Find sin(s+t) and (s-t) if cos(s)= 1/5 and sin(t) = 3/5 and s and t are in quadrant 1. =Sin(s)cos(t) + Cos(s)Sin(t) =Sin(1/5)Cos(3/5) + Cos(-1/5)Sin(3/5) = 0.389418 Sin(s-t) =sin(s)cos(t) - cos(s)sin(t) =sin(-3/5)cos(1/5) - cos(1/5)sin(3/5) …

More Similar Questions