Question

The lengths of side b is 15cm, c is 24cm and a is 18cm. How do you calculate the angle B (which is opposite side b)?

Answer 1

`38.62^@`

Explanation:

Use the law of cosine of solving triangles :

`b^2=a^2+c^2-2*a*c*cosB`

`=> 15^2=18^2+24^2-2*18*24*cosB`

`=> CosB = (18^2+24^2-15^2)/(2*18*24)=0.78125`

`=> B = cos^-1(0.78125)=38.62^@` (two decimal place)