Math Analysis

Use the half-angle formula to find the exact value of cos(x/2) when tanx = -5/8 and x is in quadrant IV. (| is a radical)

==> I got sqrt((89 + 8sqrt(89))/178). Is this correct? I hope my answer is easy to read..

  1. 👍 0
  2. 👎 0
  3. 👁 85
asked by Emily
  1. The answer is correct.
    In fact, you have nicely rationalized the denominator, which is expected of students.
    You could also express the answer as:
    cos(x)=sqrt((1/2)+4sqrt(89)/89)
    if it appeals to you.

    1. 👍 0
    2. 👎 0
    posted by MathMate

Respond to this Question

First Name

Your Response

Similar Questions

  1. trig

    Use a half-angle formula to find the exact value of cos 5ð/12

    asked by Steve on December 16, 2009
  2. MATH

    1.)Find the exact solution algebriacally, if possible: (PLEASE SHOW ALL STEPS) sin 2x - sin x = 0 2.) GIVEN: sin u = 3/5, 0 < u < ï/2 Find the exact values of: sin 2u, cos 2u and tan 2u using the double-angle formulas. 3.)Use the

    asked by MAKITA on April 10, 2009
  3. trig

    use a half angle formula to find the exact value of cos 75 degree

    asked by lan on May 8, 2011
  4. Math

    cotθ=3, cos

    asked by Anonymous on January 8, 2018
  5. trig

    half angle formula to find exact value cos 112.5 degree

    asked by Billy on March 8, 2016
  6. Algebra

    Find the exact value of sin(u/2), cos(u/2), and tan(u/2) using the half-angle formula, given that cscu = -5/3 and π < u < 3π/2

    asked by Amanda on February 18, 2018
  7. Mathmatics

    a. Use the formulas for lowering powers to rewrite the expression in terms of the first power of cosine: (cos^4)x (or cos*x to the 4th power) b.Use an appropriate Half- Angle Formula to Find the Exact value of the expression: 1.

    asked by Tricia on March 3, 2014
  8. Please help Math

    a. Use the formulas for lowering powers to rewrite the expression in terms of the first power of cosine: (cos^4)x (or cos*x to the 4th power) b.Use an appropriate Half- Angle Formula to Find the Exact value of the expression: 1.

    asked by Tricia on March 3, 2014
  9. Trig

    If cosx = 10/19 an pi < x < 2pi, find the exact value of cos x/2 Use the double angle formula. Cos 2Y= sin^2 Y - cos^2Y = 1-2Cos^2 Y. let y= x/2, and 2Y=x

    asked by Ashley on April 14, 2007
  10. Algebra II

    1) Find the exact value of cos 105 degrees by using a half-angle formula. 2)Find the solution of sin 2theta = cos theta if 0 degrees

    asked by Lucy on April 19, 2008

More Similar Questions