SOLUTION: If cos A = 1/3 , find sin (A/2) if ∠A is ACUTE.

Algebra ->  Trigonometry-basics -> SOLUTION: If cos A = 1/3 , find sin (A/2) if ∠A is ACUTE.       Log On


   

Question 1137994: If cos A = 1/3 , find sin (A/2) if ∠A is ACUTE.
Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
.
Use trigonometric formula of half argument


    sin%28A%2F2%29 = sqrt%28%281-cos%28A%29%29%2F2%29.


Substitute here cos(A) = 1%2F3.  You will get


    sin%28A%2F2%29 = sqrt%28%281-1%2F3%29%2F2%29 = sqrt%28%28%282%2F3%29%29%2F2%29 = sqrt%281%2F3%29 = sqrt%283%29%2F3.     ANSWER

Solved.

-----------------

On trigonometric formulas see the lessons
    - FORMULAS FOR TRIGONOMETRIC FUNCTIONS
in this site.