The formula for cosine is adj/hyp. For angle B, 10 is the adjacent and 24 is the opposite. The hypotenuse ( in this case, 26) is the longest side. the ratio for angle b would be 10/26.
Answer:
Option B. 
Step-by-step explanation:
we know that
The area of a circle is equal to

we have

substitute

Remember that
radians subtends the complete circle of area 
so
by proportion
Find the area of the related sector for a central angle of
radians
Let
x------> the area of the related sector

Angle PTG = arccos((18^2 + 13^2 - 27^2) / (2 x 18 x 13)) = arccos(-236 / 468) = arccos(-0.5043) = 120 degrees.
The triangle is an obtuse triangle (because one of the angles is greater than 90 degrees) and a scalene triangle (because all the sides are not equal).