In triangle ABC, if a = 8.75a=8.75 centimeters, c = 4.26c=4.26 centimeters, and m/_BmB is 87° what is the length of b to two decimal places?

1 Answer
Aug 13, 2018

:.b~~9.53 " cm"

Explanation:

We know that ,

color(red)("cosine Rule : " cosB=(c^2+a^2-b^2)/(2ca))

:.2cacosB=c^2+a^2-b^2

:.b^2=c^2+a^2-2cacosB...to(1)

We have ,

a=8.75" cm" , , c=4.26 " cm" and B=87^circ

Using (1) we get

b^2=(4.26)^2+(8.75)^2-2(4.26)(8.75)cos87^circ

:.b^2=18.1476+76.5625-74.55(0.0523)

:.b^2~~90.81135

:.b~~9.529 cm