posted by .

Given cos x=2/3 and 3pi/2<x<2pi, find the exact value of cos2x?

  • Pre-Calc/Math -

    cos2x = 2cos^2(x) - 1 = 2(4/9)-1 = 8/9-1 = -1/9

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. pre-calc

    Can someone help me find the exact value of 4csc(3pi/4)-cot(-pi/4)?
  2. Pre-Calculus-check answers

    State the period and phase shift of the function y=-4tan(1/2x + 3pi/8) a) 2pi, -3pi/4 b) pi, 3pi/8 c) 2pi, 3pi/8 d) pi, -3pi/8 Answer: d 2) What is the equation for the inverse of y=cos x+3: a) y=Arccos(x+3) b) y=Arccos x-3 c) y=Arccos …
  3. Trigonometry

    a. Find the exact value of sin (theta - pi/6) b. Find the exact value of cos (theta - pi/4) c. For what numbers x, -2pi less than or equal to x less than or equal to 2pi does cos x = -1 d. What is the range of the cosine function?
  4. Pre-Calc/Math

    If cosx= -2/3 and pi/2, find the exact value of cos(pi/3-x)
  5. trig

    Solve cos x-1 = sin^2 x Find all solutions on the interval [0,2pi) a. x=pi, x=pi/2, x= 2pi/3 b. x=3pi/7, x=pi/2, x=2pi/3 c. x=3pi/7, x=3pi/2, x=3pi/2 d. x=pi, x=pi/2, x=3pi/2
  6. Math (Pre-calc)

    I need to know how to solve this for my review questions. Thanks! The wheel on a racing bike have a radius of 14 in. How fast is the cyclist traveling in mph if the wheels are turning at 280 revolutions per minute. find the exact value …
  7. Math Answer Check

    1. Find the exact value of the expression. cos pi/16 * cos 3pi/16 - sin pi/16 * sin 3pi/16 My ans: sqrt2/2 2. Find the exact value of the sin of the angle. 17pi/12 = 7pi/6 + pi/4 My ans: (sqrt2 - sqrt6)/4
  8. Pre calc

    Let sin u=-8/17 and cos v= 12/13, with pie<u<3pie/2. Find the exact value of cos(u+v)
  9. Pre calc

    Evaluate the expression given that cosine a=4/5 with 0<a<pi/2 and sin b=-15/17 with 3pi/2< b<2pi
  10. Trig

    Find all solutions of the equation in the interval [0,2pi) 2 cos^2 x-cos x = 0 -2cos^2 + cosx + 0 (x+1/2) (x+0/2) (2x+1) (x+0) -1/2,0 2Pi/3, 4pi/3, pi/2, 3pi/2 my teacher circled pi/2 and 3pi/2 What did I do wrong?

More Similar Questions