SOLUTION: if cos A = 3/5 and angle A is acute find sin 1/2 A

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Question 814446: if cos A = 3/5 and angle A is acute find sin 1/2 A
Answer by lwsshak3(11628) About Me  (Show Source):
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if cos A = 3/5 and angle A is acute find sin 1/2 A
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sinA=√(1-cos^2A)=√(1-9/25)=√(16/25)=4/5
sin(A/2)=√((1-cosA)/2)=√((1-(3/5))/2)=√((2/5)/2)=√(2/10)=√(1/5)=1/√5=√5/5
Calculator check:
sinA=4/5
A≈53.13˚
A/2≈26.56˚
sin(A/2)≈sin(26.56)≈0.447..
Exact value as computed=√5/5≈0.447..