Trig Help

posted by .

Given that cos2x=7/12 and "270 equal or < 2x equal or < 360", find sinx.

Please help and Thank you

  • Trig Help -

    In these type of quesstions it usually asks for the "exact" value of ....

    cos 2x = 7/12

    cos 2x = 1 - 2sin^2 x
    2 sin^2 x = 1 - cos 2x = 1 - 7/12 = 5/12
    sin^2 x = 5/24
    sin x = ± √(5/24)
    but 270 < 2x ≤ 360
    135 ≤ x ≤ 180 ---> x in in I or II, so
    sinx = +√5/√24 = √30/12

  • Trig Help -

    how did you get the ã30/12?

  • Trig Help -


    when you rationalize the denominator you times both top and bottom by sqrt(6) only not the 2 right?

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. trig

    sinx = 4/5 and x terminates in Quadrant II Find sin2x and cos2x How to get the answers, which are sin2x = -24/25, cos2x = -7/25?
  2. trig

    cotx = -2 and 0 less than or equal to x less than or equal to pi Find sin2x and cos2x How to get the answers of sin2x = -4/5, cos2x = 3/5?
  3. Trig--check answer

    Solve the equation of the interval (0, 2pi) cosx=sinx I squared both sides to get :cos²x=sin²x Then using tri indentites I came up with cos²x=1-cos²x Ended up with 2cos²x=1 Would the answer be cos²x=1/2?
  4. trig

    1/sinx = sinx+cosxcotx it's a proof and I have to make them equal to each other. Please help!
  5. Trig

    I'm confused on how to determine what the end result angles are for a trigonometric identity (I get how to find the value of sin, cos, etc., and I know how to find the reference angle. I just don't know how to determine further angles …
  6. trig

    how do you solve: find cos2x if sinx is equal to 1/5
  7. Trig (Last URGENT)

    sin2x+cosx=0 , [-180,180) = 2sinxcosx+cosx=0 = cosx(2sinx+1)=0 cosx=0 x1=cos^-1(0) x1=90 x2=360-90 x2=270 270 doesn't fit in [-180,180) what do I do?
  8. Trig Help

    Prove the following: [1+sinx]/[1+cscx]=tanx/secx =[1+sinx]/[1+1/sinx] =[1+sinx]/[(sinx+1)/sinx] =[1+sinx]*[sinx/(sinx+1)] =[sinx+sin^2x]/[sinx+1] =[sinx+(1-cos^2x)]/[sinx+1] =?
  9. Calculus

    In the interval (0 is less than or equal to x which is less than or equal to 5), the graphs of y=cos(2x) and y=sin(3x) intersect four times. Let A, B, C, and D be the x-coordinates of these points so that 0<A<B<C<D<5. …
  10. Math Help

    Hello! Can someone please check and see if I did this right?

More Similar Questions