SOLUTION: In the diagram, the length of Arc AB is (3y-9)times pi. What is the value of y? The circle's center from a to b is 144 degrees and has a radius of 12. It is hard to

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The length of an arc, S is given by S=rA where r is the radius and A is the angle IN RADIANS:

So, we have 144 degrees. What is this in radians?

Start with one thing you NEED to learn:
360 degree = 2 radians
--> 1 degree = radians
--> 144 degrees = radians

You can simplify this out a bit if you wish here:



Right then, S=rA
-->
-->

So, this is equivalent to

so,




--> y = 6.2


jon.