MATH ANALYSIS

I need help solving this problem algebraically, but I need to learn step by step!!
Thanks so much

cos 2x=cos x

How do I do it?

  1. 👍
  2. 👎
  3. 👁
  1. you should know that
    cos 2x = 2cos^2 x - 1

    so we have
    2cos^2 x - 1 = cosx
    2cos^2 x - cosx - 1 = 0
    (2cosx + 1)(cosx -1) = 0
    cosx = -1/2 or cosx = 1

    x = 120° or 240° or x = 0 or 360
    in radians
    x = 0, 2π/3, 4π/3, 2π

    1. 👍
    2. 👎
  2. Thanks!

    1. 👍
    2. 👎

Respond to this Question

First Name

Your Response

Similar Questions

  1. Chem 2

    Propane (C3H8) burns in oxygen to produce carbon dioxide and water vapor. The balance equation for this reaction is C3H8 + 5O2 ----> 4H20 + 3CO2. What volume of carbon dioxide id produced when 2.8 L of oxygen are consumed? Here

  2. Algebra

    Josephine solved a quadratic equation: (x+6)^2=49. Her work is shown below. Step 1: √(x+6)^2 = √49 Step 2: x+6 = 7 Step 3: x = 7−6 Step 4: x = 1 In which step did Josephine make an error? A- step 4 B- step 1 C- step 2 D-

  3. math

    Consider the sequence of steps to solve the equation: 5(x - 3) = 7x 2 Step 1 ⇒ 10(x - 3) = 7x Step 2 ⇒ 10x - 30 = 7x Step 3 ⇒ 3x - 30 = 0 Step 4 ⇒ 3x = 30 Step 5 ⇒ x = 10 Identify the property of equality which yields

  4. chemistry

    What is the percent ionization of a 1.38 mol/L weak acid if its Ka = 2.7 x 10-6? Answer to two (2) decimal places. I know what steps to use but have difficulty applying them to the quesiton Can someone please complete the question

  1. math

    Consider the sequence of steps to solve the equation: 2(x − 4) + 6x = 9x − 10 Which step in solving this equation is justified by the Commutative Property of Addition? Given ⇒ 2(x − 4) + 6x = 9x − 10 Step 1 ⇒ 2x − 8

  2. Science

    solve the system of equations algebraically. show all your steps. y=x^2+2x y=3x+20 Can someone show me step by step on how to get the answer it's, there are answers like this that is going to be on my math test and I don'tget it.

  3. math

    George Polya has a four-step process for Problem Solving. What is the first step?

  4. Physics

    You are given vectors A = 5.0i - 6.5j and B = -2.5i + 7.0j. A third vector C lies in the xy-plane. Vector C is perpendicular to vector A and the scalar product of C with B is 15.0. Find the x and y components to vector C. Here's

  1. Math

    April rewrote a quadratic function in vertex form. h(x)=5^2-30x+30 step 1 h(x)=5(x^2-6x+ )+30 step 2 h(x)=5(x^2-6x+9)+30-45 step 3 h(x)= 5(x-3)^2+15 In which step did they make a mistake? and how? Please help

  2. CHEM

    The decomposition of nitrogen dioxide 2NO2-->2NO+O2 occurs in a two-step sequence at elevated tempatures. the first step lis NO2--> NO+O. predict a possible second step that, when combined with the first step, gives the complete

  3. Math

    I need help solving the problem not the answer. (Multiple Choice) The steps below show the incomplete solution to find the value of x for the equation 7x + 8 − 3x = −6 + 10: Step 1: 7x + 8 − 3x = −6 + 10 Step 2: 7x + 8 −

  4. chemistry

    This question I really don't get it. I tried tried tried to figure out how to start solve the problem but still couldn't figure out. So can you help me with one question PLEASE? If so, can you please explain to me how you get the

You can view more similar questions or ask a new question.