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1 answer:
Answer:
When writing this on a keyboard, you would say 2*sqrt(7)
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Explanation:
The formula we'll use is
A = 0.5*p*q*sin(R)
where R is the angle between sides p and q.
The diagram shows that p = x+4 is opposite angle P, and q = x is opposite angle Q. Convention usually has the uppercase letters be angles, and the lowercase letters as the sides.
Plug in the given values and simplify to get the following
A = 0.5*p*q*sin(R)
A = 0.5*(x+4)*x*sin(60)
A = 0.5*(x+4)*x*sqrt(3)/2 ..... use the unit circle
A = 0.25*(x^2+4x)*sqrt(3)
A = (0.25x^2+x)*sqrt(3)
Set this equal to the given area of A = sqrt(27) and solve for x
A = (0.25x^2+x)*sqrt(3)
(0.25x^2+x)*sqrt(3) = A
(0.25x^2+x)*sqrt(3) = sqrt(27)
(0.25x^2+x)*sqrt(3) = 3*sqrt(3) .... see note1 at the very bottom
0.25x^2+x = 3
(1/4)x^2+x = 3
x^2+4x = 12 .... see note2 at the very bottom
x^2+4x-12 = 0
(x+6)(x-2) = 0
x+6 = 0 or x-2 = 0
x = -6 or x = 2
A negative side length doesn't make sense, so we ignore x = -6. The only solution here is x = 2.
Since x = 2, this means we have the following side lengths so far
- p = RQ = x+4 = 2+4 = 6
- q = PR = x = 2
Now apply the law of cosines to find the missing side.
r^2 = p^2 + q^2 - 2*p*q*cos(R)
r^2 = 6^2 + 2^2 - 2*6*2*cos(60)
r^2 = 36 + 4 - 24*1/2
r^2 = 40 - 12
r^2 = 28
r = sqrt(28)
r = sqrt(4*7)
r = 2*sqrt(7)
Side PQ is exactly 2*sqrt(7) units long
This approximates to 2*sqrt(7) = 5.2915
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Footnotes:
- Note1: sqrt(27) = sqrt(9*3) = sqrt(9)*sqrt(3) = 3*sqrt(3)
- Note2: I multiplied both sides by 4 to clear out the fraction
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