Question

In ΔABC, if a = 18, b = 24, c = 30 then find the values of cosA

Answer 1

Given: a = 18, b = 24 and c = 30
∴ 2s = a + b + c
= 18 + 24 + 30
= 72
∴ s = 36

cosA = `(b^2 + c^2 - a^2)/(2bc)`

= `((24)^2 + (30)^2 - (18)^2)/(2(24)(30)`

= `(576 + 900 - 324)/(1440)`

= `(1152)/(1440)`

= `4/5`.