posted by .

Simplify (sin^2)*(67.5deg) - (cos^2)*(67.5deg) and then evaluate exactly.

  • Trig -

    well, cos 2x = cos^2 x - sin^2 x, so what do you think?

    If you end up with 1/√2 you are correct.

  • Trig -

    How exactly do you get there though? I tried to follow a similar homework problem and got:

    = (cos^2)*(67.5deg) - (sin^2)*(67.5deg)
    = cos(2*67.5deg)
    = cos135deg
    = -√2/2

  • Trig -

    note that the problem was

    = -cos(135)

    my hint was not intended to make you forget what was originally asked. :-)

    And, I know lots of folks hate roots in the denominator, but I see no reason why √2/2 is better than 1/√2. Just mt preference

  • Trig -

    Thank you very much!

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. trig

    Reduce the following to the sine or cosine of one angle: (i) sin145*cos75 - cos145*sin75 (ii) cos35*cos15 - sin35*sin15 Use the formulae: sin(a+b)= sin(a) cos(b) + cos(a)sin(b) and cos(a+b)= cos(a)cos(b) - sin(a)sin)(b) (1)The quantity …
  2. algebra

    Can someone please help me do this problem?
  3. trigonometry

    Write the function in terms of the cofnction with an acute angle. tan 18degrees A. sec18deg B. cot18deg C. cot72deg D. cot108deg find a solution for the equation. sin(2theta+20deg) = cos(3theta-5deg) thnkks:))
  4. TRIG!

    Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6 x=1 - (3/4)sin^2 2x work on one side only! Responses Trig please help! - Reiny, Monday, February 23, 2009 at 4:27pm LS looks like the sum of cubes sin^6 x + cos^6 …
  5. Precal

    I do not understand how to do this problem ((sin^3 A + cos^3 A)/(sin A + cos A) ) = 1 - sin A cos A note that all the trig terms are closed right after there A's example sin A cos A = sin (A) cos (A) I wrote it out like this 0 = - …
  6. trig 26

    simplify to a constant or trig func. 1. sec ²u-tan ²u/cos ²v+sin ²v change expression to only sines and cosines. then to a basic trig function. 2. sin(theta) - tan(theta)*cos(theta)+ cos(pi/2 - theta) 3. (sec y - tan y)(sec y + …
  7. Inverse Functions & Trig. Equations

    7. Evaluate sin[sin^-1(-1/2)]. a. 1/2 b. ð /6 c. -1/2 d. - ð /6 8. Evaluate cos[tan^-1(5/12)]. a. 12/13 b. 12/5 c. 5/12 d. 5/13 9. Evaluate cos[sin^-1(-3/5)]. a. -4/5 b. 5/4 c. 4/5 d. -3/4
  8. trig

    Use a sum or difference identity to find the exact value. tan 25deg + tan 5deg / 1-tan 25deg tan 5deg
  9. Trignometry

    solve the triangle. B=77.0deg b=13.95 a=20.6 I got A=38.5deg C=64.5deg c=34.55
  10. Physics

    A box (mass=34kg) is set on an incline (angle=36.5 degrees), attached to a string. The box is let go slowly with a tension of 205N on the string, and starts sliding down with an acceleration of 0.12m/s^2. What was the coefficient of …

More Similar Questions