In degrees: 3π/4 radians = 135°
Angle of x=135° is in the 2nd Quadrant and has negative cos x values and positive sin x values.
cos 135° = cos ( 90° + 45°)= - sin 45° =

sin 135° = sin ( 90° + 45° ) = cos 45° =

. You can also see the graph in the attachment.
Answer:
He has to pay 15% as that is 32 and more than $25
Step-by-step explanation:
If you take 15% out of 216 it will become 32.
Use Pythagorean Theorem:
a² + b² = c²
"a" is one side of the right triangle.
Its length is: radius of larger circle minus radius of smaller circle: (11 - 3 = 8)
The distance between the center of the circles creates the hypotenuse (17)
8² + b² = 17²
b² = 225
b = 15
Answer: the length of the common external tangent is 15.