Trigonometry
posted by Lucy X
Hi, I need help with this question:
Use the addition and subtraction formulas ti fubd the exact values of the trigonometric ratios:
cos(7pi/12)
Okay, I'm just having trouble with a rather basic part of the question...
I wrote cos(pi/4 + pi/3), but now I realized that the trig ratio is negative. How do I write 7pi/12 as the sum/difference of two trig ratios?
Respond to this Question
Similar Questions

CALCULUS
If cos(t)=–7/9, find the values of the following trigonometric functions. Note: Give exact answers, do not use decimal numbers. The answer should be a fraction or an arithmetic expression. a) cos (2t) b) sin (2t) c) cos(1/2) d) sin … 
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 … 
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 … 
Trigonometry
How do you find the exact value of cos 7pi/12 without using a calculator to change radian to degree 
PreCalc
1) Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one number. cos 12° cos 18° − sin 12° sin 18° And Find its exact value. 2) Use an Addition or Subtraction Formula to write the … 
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 … 
Trigonometry
Use the trigonometric subtraction formula for sine to verify this identity: sin((π / 2) – x) = cos x 
PreCal
Use an Addition or Subtraction Formula to write the expression as a trigonometric function of one number. (tan(74°)tan(14°))/(1+tan(74°)tan(14°)) =__________ Find it's exact value (not decimal form) =__________ Note: A similar … 
Math
An angle θ satisfies the relation csc θ cos θ = 1. A) Use the definition of the reciprocal trigonometric ratios to express the left side in terms of sin θ and cos θ. B) What is the relation between sin θ and cos θ for this … 
Math
Consider ∠C such that sin C = 7/25 a) What are the possible quadrants in which ∠C may lie?