I believe that the question was created by
Manhattan Prep to illustrate strategic guessing (I could be wrong, it was a while ago). Also, since we are estimating, we can make some approximate guesses.
I’m a triangle, the sides of a triangle are, in a sense, proportional to the angles of the triangle. The sides are in fact in a constant proportion to the Sine of each angle’s degree measure - the angle opposite each Side
Side a / (Sin Angle Opp a) = Side b / (Sin Angle Opp b) = Side c / (Sin Angle Opp c)
(1st) given we have an isosceles triangle, the other 2 angle measures both equal = (135/2) = 67.5 degrees
(2nd) The “Sine” Proportion can be taken. For each side and its opposite angle, the following proportion holds true:
Sqrt(3) / (Sine 45 deg.) = (X) / (Sine 67.5 deg.) = (X) / (Sine 67.5 deg.)
The Sine of 45 degrees = (1) / (sqrt(2))
We can use the Sine of 60 degrees to approximate the Sine of 67.5 degrees, since it easier to find and since 60 degrees is close to 67.5 degrees
The sine of 60 degrees = sqrt(3) / 2
Substituting we have:
[ sqrt(2) ] / [ 1/sqrt(2) ] = [ x ] / [ sqrt(3) / 2]
In the right hand side of the equation, the square root of 2 squared = 2——-you are left with:
2 = (2x) / (sqrt(3))
—cancel the 2 in the NUM on each side of the equation—
1 = X / (sqrt(3))
-cross multiply-
X = sqrt(3)
Since this is only an approximation and not the actual value or X, I suspect there are other ways to estimate the answer. It’s too coincidental that the estimate found happened to be the exact value of the correct answer approximation.
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