Trig
posted by Help .
Use the halfangle formulas to come up with an exact expression for each function value below. You do not have to simplify your answers.
cos(pi/16)

Trig 
drwls
cos (x/2) = sqrt[(1/2)(1 + cosx)]
cos(pi/16) = sqrt[(1/2)(1 + cos(pi/8)]
cos(pi/8) = sqrt[(1/2)(1 + cos(pi/4)]
= sqrt[(1/2)(1 + sqrt2/2] = 0.92388..
cos(pi/16) = sqrt[(1/2)*1.92388]
= 0.980785..
Writing it in exact form would be a bit messy, but I hope you see how it can be done
Respond to this Question
Similar Questions

trig
Use halfangle formulas to find the exact value for the following cot 75 degrees 
MATH
1.)Find the exact solution algebriacally, if possible: (PLEASE SHOW ALL STEPS) sin 2x  sin x = 0 2.) GIVEN: sin u = 3/5, 0 < u < ï/2 Find the exact values of: sin 2u, cos 2u and tan 2u using the doubleangle formulas. 3.)Use … 
trig
Use a halfangle formula to find the exact value of cos 5ð/12 
Trignometry questions EASY HELP
1. Which is a solution to the equation below? 
TRIG/ALGEBRA
1) Find the exact value. Use a sum or difference identity. tan (15 degrees) 2) Rewrite the following expression as a trigonometric function of a single angle measure. cos 3x cos 4x  sin 3x sine 4x 
Math Trig
1. Determine the exact value of cos^1 (pi/2). Give number and explanaton. 2. Determine the exact value of tan^1(sq. root 3). with explanation. 3. Determine exact value of cos(cos^1(19 pi)). with explanation. 4. Determine the exact … 
Mathmatics
a. Use the formulas for lowering powers to rewrite the expression in terms of the first power of cosine: (cos^4)x (or cos*x to the 4th power) b.Use an appropriate Half Angle Formula to Find the Exact value of the expression: 1. tan … 
Please help Math
a. Use the formulas for lowering powers to rewrite the expression in terms of the first power of cosine: (cos^4)x (or cos*x to the 4th power) b.Use an appropriate Half Angle Formula to Find the Exact value of the expression: 1. tan … 
Trig/Precalc
So I have two questions that have been puzzling me for quite some time and would really appreciate any help with either of them! (a) There are four positive intergers a, b, c, and d such that 4cos(x)cos(2x)cos(4x)=cos(ax)+cos(bx)+cos(cx)+cos(dx) … 
PreCalc
I am really struggling with how to do these problems, I posted them a few minutes ago but the answers/work shown was incorrect. 1) a) Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one …