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