Pre Cal

2cos 4theta + 1 = 0

i know how to find the degrees (the last step of the problem), but i don't know how to start the problem. Could someone please show me the steps?

I assume you mean cos (4 theta) and not
(cos theta)^4

cos (4 theta) = -1/2
The angles with a cosine equal to -1/2 are: 120 and 240 degrees, and also 480 and 600 degrees, and 840 and 960 degrees etc (Just adding 360 degrees to previous answers). . Since that is 4 theta, divide any of those numbers by 4 for theta values that are solutions.
THETA = 30, 60, 120, 150, 210, 240...degrees

  1. 👍 0
  2. 👎 0
  3. 👁 167
asked by Marie

Respond to this Question

First Name

Your Response

Similar Questions

  1. trig

    find the single term of cos^2 4theta - sin^2 4theta

    asked by jenna on May 16, 2012
  2. math

    i don't know how to work these problems out so i'll just pick a random one out from my home work and if someone could explain it to me step by step that would be very helpful. Solve the tragicomic expression for all answers

    asked by Kathryn on May 15, 2008
  3. Math

    Find one solution for each equation. 1. cos 4theta = sin theta 2. tan 4theta = cot (20^0 + 20) Write the function sin (B + 35^0) in terms of its cofunction.

    asked by Annika on September 25, 2013
  4. math

    how do you get sin(4theta)/1+cos(4theta) to equal tan(2theta)

    asked by John on January 12, 2011
  5. Chemistry (Making sure

    For how many kilojoules are required to change 44.0g of ice at -12.0 degrees C to water at 85.0 degrees C? Would this be correct: Step 1: (2.10 J/g degrees C)(44g)(12 degrees C) = 1108.8J = 1.1088kJ Step 2:

    asked by Anonymous on May 20, 2010
  6. Calculus

    what is the limit of g(theta)= tan(4theta)/4theta.

    asked by Ashley on September 12, 2012
  7. Trigonometry

    Need help solving problems using the Trigonometric Identities: 8cos^4 thet=cos4theta+4cos2theta+3 I am a bit unsure how to solve it. I am aware that the first step I must take is to simplify the problem and then use the Product to

    asked by sierra on April 23, 2007
  8. precal

    4=2cos(pi/6t-2pi/3)+4 How do i solve this step by step ith justification for each step? super frustratd thankyou

    asked by wendell on June 8, 2012
  9. math

    the problem is 2cos^2x + sinx-1=0 the directions are to "use an identity to solve each equation on the interval [0,2pi). This is what i've done so far: 2cos^2x+sinx-1=0 2cos^2x-1+sinx=0 cos2x + sinx =0 1 - 2sin^2x + sinx = 0

    asked by alex on April 7, 2008
  10. math

    cosA= 5/9 find cos1/2A are you familiar with the half-angle formulas? the one I would use here is cos A = 2cos^2 (1/2)A - 1 5/9 + 1 =2cos^2 (1/2)A 14/9 =2cos^2 (1/2)A cos (1/2)A = √(7)/3

    asked by Anonymous on May 3, 2007

More Similar Questions