Pythagorean Theorem!!
A^2+B^2=C^2
Your a is your line bc, and your c is your line ac (or your hypotenuse).
Input for those values.
(4)^2+B^2=(6)^2
16+B^2=36
Solve.
16+B^2=36
-16. -16
________
B^2=20
Then once you simplify to where you have a variable squared on one side, find the square root of both sides.
-/(b^2)=-/(20)
The square root of b squared is b, and the square root of 20 is 4.47.
B=4.47 centimeters
Please note that is a rounded answer within the decimal count given.