1. Questions

Trigonometry

cos²a + cos²(a+120°) + cos(a-120°) = 3/2

  1. 👍
  2. 👎
  3. 👁
Kewal

  1. after some of those others you posted, this one is pretty mechanical
    cos 120° = -1/2
    sin 120° = √3/2

    (-1/2)^2 + (cosa * (-1/2) - sina*(√3/2))^2 + (cosa * (-1/2) + sina*(√3/2))^2

    1/4 + 1/4 (cos^2a + 2√3 sina*cosa + 3sin^2a) + 1/4 (cos^2a - 2√3 sina*cosa + 3sin^2a)

    1/4 (1 + 2cos^2a + 6sin^2a)
    1/4 (1 + 2 + 4sin^2a)

    3/4 + sin^2a = 3/2
    sin^2a = 3/4
    sina = ±√3/2

    a = pi/3, 2pi/3, 4pi/3, 5pi/3

    1. 👍
    2. 👎
    Steve

Respond to this Question

First Name

Your Response

Similar Questions

  1. Algebra

    1.Mary is selling her craft to earn money she sells her bracelets for $6 and her necklaces for $10 her goal is to make at least $120 in sales which of the following represents three possible solutions to the problem A.6x+10y=120

  2. Calculus

    The cost of producing x units of a certain commodity is C(x)=1000+5.70x+0.7x^2 . What is the average rate of change of C with respect to x when the production level is raised from x = 100 to x = 120 and when the production level

  3. math

    cos^6A-sin^6A=cos2A(1-1÷4sin^2 2A) Prove

  4. Calculus

    Find d^5/dx^5 g(x) for g(x)=sinx+5x^4 A. cos x B. sin x + 120 C. -cos x +20x^3 D. -cos x + 120 x E. sin x

  1. maths-TRIGNOMETRY

    show that: 2^5 cos^2a sin^4a=cos6a-2cos4a- cos2a + 2

  2. Math (Trigenometry)

    Find two positve real numbers whose product is a maximum and whose sum of the first number and four times the second number is 120. This is as far as I've gotten in solving it. *first number is x. *second number is y. *xy=maximum,

  3. math

    In Lewis Carroll's Through The looking Glass, Tweedledum says, "the sum of your weight and twice mine is 361 pounds". Tweedledee replies, "The sum of your weight and twice mine is 362 pounds". Find both weights. ONLY AN ALGEBRAIC

  4. Science

    What is the current in the 30-ohm heating coil of a coffee maker that operates on a 120-volt circuit? Would be 120/30?

  1. math (cant figure it out)

    3. A number cube is rolled 120 times. The number 4 comes up 47 times. What is the experimental probability of rolling a 4? What is the theoretical probability of rolling a 4? A. 47/120; 1/30*****? B. 47/120; 1/6 C. 4/47; 1/6 D.

  2. math

    what is the value of x in the diagram? A. 30* B. 60* C. 90 D. 120. (The angle of the figure is 120*)

  3. Trigonometry

    Prove that sin(n+1)Asin(n-1)A + cos(n+1)Acos(n-1)A = cos2A

  4. Studying for Pre Cal exam

    Find the fourth roots of − 1/2 + (square root)3/2 i Write the roots in trigonometric form. A - w 1=cos(35°)+isin(35°) w2 =cos(125°)+isin(125°) w3 =cos(215°)+isin(215°) w4 =cos(305°)+isin(305°) B - w1

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