The segment GH and GI are tangent

  OG = 8.7

Step-by-step explanation:

The angle a tangent makes with a radius at the point of tangency is a right angle. That means ΔOGH is a right triangle.

The tangents to a circle from an external point are congruent, so GH = GI = 6.3. Now we know the sides of the right triangle are of lengths 6 and 6.3. The hypotenuse, OG is found using the Pythagorean theorem.

  OG² = OH² +GH²

  OG² = 6² +6.3² = 75.69

  OG = √75.69 = 8.7

The length of OG is 8.7 units.

Additional comment

You might recognize this triangle as a 0.3 multiple of the Pythagorean triple (20, 21, 29).

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12