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There is EXTREMELY SIMPLE solution.
From the diagram, we have an isosceles triangle AXO with equal sides lengths | AX | = | OX |.
The base AO of this triangle is 16 units long, since it is the hypotenuse of the (30° - 60° - 90°) triangle AOT.
The angle A is 30°.
Draw the altitude XZ in the triangle AXO.
Then you will get right angled triangle AXZ with the long leg AZ of the length of 8 = 16/2 units and the angle A of 30°.
Thus cos(A) = cos(30°) = = ,
which implies m = = = 9.237 units approximately, if you want to have the numerical value.
ANSWER. m = = 9.237 (approximately).
Solved.