SOLUTION: Suppose A is an acute angle and cos A = 1/3. Find sin 2A and cos 1/2A Make sure to show work.

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Question 1138170: Suppose A is an acute angle and cos A = 1/3. Find sin 2A and cos 1/2A
Make sure to show work.
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
cos =1/3, so adjacent side is 1 and hypotenuse is 3
therefore, sine is 2*sqrt(2)/3 (70.52 deg)
sin 2A=2 sinA*cosA
sin 2A=2*2 sqrt(2)/3*1/3
=4 sqrt(2)/9
cos (A/2)= +/- sqrt((1+cos A)/2), use +
= sqrt(4/3/2)=sqrt(2/3)=sqrt(6)/3