Question

I need help ASAP on Tangent Circles!!

Answer 1

I will solve one for you to get you a idea so next u can solve all
To know whether line is tangent toa circle or not we should know that that line is a tangent line of a circle if it intersects circle at single point.
and this will always be perpendicular at radius
so in problem
1)

diameter is given 7.5 
and u can see they make a right triangle ABC if that is perpendicular so segment  AB is tangent to a circle.
Lets see by applying Pythagorean Theorem
this is method we can say that this is in fact a right triangle

a^2=b^2=c^2
a,b are shorter side c is longer side
(7.5)^2+(8)^2=(17)^2
 56.25+64=289
120.25=289
both are not equal so they are not forming right triangle so segment AB is not a tangent line.