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Question
In ΔABC, ∠A = 90°. If AB = 5 units and AC = 12 units, find: cos C
Solution
In ΔABC,
BC2 = AB2 + AC2
⇒ BC = `sqrt("AB"^2 + "AC"^2)`
⇒ BC = `sqrt(5^2 + 12^2)`
= `sqrt(169)`
= 13
AC = 12 units
BC = 13units
AB = 5units
cos C
= `"Base"/"Hypotenuse"`
= `"AC"/"BC"`
= `(12)/(13)`.
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