The measure of EF from the given diagram is 6 units
Secant secant theorem
The theorem states that if two secants are drawn from an external point to a circle, then the product of the measures of one secant's external parts is the same as the product of the other external part.
Mathematically according to the given figure;
4(4+2x) = 5(5+x)
Expand
16 + 8x = 25 + 5x
Collect the like terms
8x - 5x = 25 - 16
3x = 9
Divide both sides by 3
3x/3=. 9/3
x = 3
Find EF
EF = 2x
EF = 2(3) = 6
Hence the measure of EF from the given diagram is 6 units
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