PLEASE HELP?

enter image source here

1 Answer
Apr 21, 2018

I got #15.8cm#

Explanation:

If AB and BC are tangent they should form an angle of #90^@# with the radius:
enter image source here
Using trigonometry I can analize the triangle AOB and find angle #alpha# by writing:

#4=10cos(alpha)#

so that:

#alpha=arcos(4/10)=66.4^@#
so that the total angle will be:

#2alpha=132.8^@#

the angle #theta# will be:

#theta=360^@-132.8^@=227.2^@# corresponding to #3.96# radians

the arc length #s# will be (angle in radians):

#s=rtheta=4*3.96=15.8cm#