precal

posted by .

when solving for all solutions how do I work out this problem: cos4(alpha)=cos2(alpha)
and when verifying each identity how do I complete this problem: sin (alpha/2)=sec alpha -1/2sin (alpha/2)sec alpha

  • precal -

    cos4x = cos2x
    2cos^2(2x)-1 = cos2x
    2cos^2(2x)-cos(2x)-1 = 1
    (2cos2x+1)(cos2x-1) = 0
    so, cos2x = -1/2 or 1
    cos 2pi/3 = cos 4pi/3 = -1/2
    cos 0 = 1

    as for the identity, I get the feeling there's a typo, because secx appears twice on the right.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. trig

    express 20sin theta + 4 cos theta as R sin(theta + alpha) R sin(theta + alpha) = R cos(alpha)sin(theta) + R sin(alpha)cos(theta) ----> Rcos(alpha) = 20 Rsin(alpha) = 4 The x-y coordinates of a point on a circle of radius R that …
  2. trig

    Please find sin (alpha/2) and cos (alpha/2) sec alpha = 3, -pi/2 < alpha < 0
  3. trig

    FInd the exact value pf the 6 trig function of alpha Given: point (-2,-6) on the terminal side of the angle in standard position sin alpha cos alpha tan alpha sec alpha csc alpha cot alpha
  4. Trigonometry

    Find the counterexample to shows that the equation sec (alpha) - cos (alpha) = sin (alpha) sec (alpha) is not an identity. Please explain.
  5. trig

    evaluate the following in exact form, where the angeles alpha and beta satisfy the conditions: sin alpha=4/5 for pi/2 < alpha < pi tan beta=7/24 for pie < beta < 3pi/2 answer choices A. sin(beta+alpha) B. tan(beta-alpha) …
  6. Math ( Polynomial )

    This time three questions - 1. If (x^2 - 1 ) is a factor of polynomial ax^4 + bx^3 + cx^2 + dx + e, show that a + c + e = b + d = 0. 2. Let R1 and R2 be the remainders when polynomials x^3 + 2x^2 - 5ax - 7 and x^ 3 + ax^2 - 12 x + …
  7. Math ( Polynomial )

    This time three questions - 1. If (x^2 - 1 ) is a factor of polynomial ax^4 + bx^3 + cx^2 + dx + e, show that a + c + e = b + d = 0. 2. Let R1 and R2 be the remainders when polynomials x^3 + 2x^2 - 5ax - 7 and x^ 3 + ax^2 - 12 x + …
  8. Math

    If alpha and beta are the zeros of the polynomial ax^2 + bx + c then evaluateA. (alpha)^2 / beta + (beta)^2 / alpha B. alpha^2 .beta + alpha.beta^2 C. 1/(alpha)^4 + 1/(beta)^4. Please work the complete solution.
  9. mathematics

    If cos 9 alpha = sin alpha 9 alpha < 90 degree then 5 alpha =
  10. algebra

    if sin alpha is 0.28° where 0° is less than or equal to alpha less than or equal to 90°, evaluate cos alpha, tan alpha, sec alpha, cosec alpha and cot alpha. please help, it's urgent.

More Similar Questions