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motikmotik
3 years ago
8

If cos A = 1/3 , then what is the positive value of sin 1/2​A, in simplest radical form with a rational denominator?

Mathematics
1 answer:
wolverine [178]3 years ago
5 0

Answer:

Step-by-step explanation:

You should remember from theory (one is the formula of the cosine of the double angle, and the other is the classic sum of squares being 1). cos A = cos^2 \frac A2 - sin^2 \frac A2 = 1- 2sin^2 \frac A2

At this point let's grab the first and last step of the chain, replacing values:

\frac 13 = 1-2sin^2\frac A2 \rightarrow 2sin^2 \frac A2 =\frac23\\sin^2 \frac A2 = \frac13 \rightarrow sin \frac A2 = \frac{1}{\sqrt3} = \frac{\sqrt3}{3}

Last passage you multiply top and bottom by the square root of 3 to rationalize.

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V=1/3 πr²h
plugging in the values, v=88π, h=8 ft
step 1
88π1/3πr²(8)
step 2
88π=8/3πr²
step 3
 divide both sides by π
88=8/3r²
multiply both sides by 3/(8)
88(3/8)=r²
step 4
simplify
33=r²
step 5 
get the square root
r=√33

Thus the mistake that Fatima made was:
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3 years ago
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