Question

From the given figure, find the values of cos C

Answer 1

In the right ΔABD,

AD² = AB² – BD²

= 13² – 5²

= 169 – 25

= 144

AD = `sqrt(144)`

= 12

In the right ΔADC,

AC² = AD² + DC²

= 12² + 16²

= 144 + 256

= 400

AC = `sqrt(400)`

= 20

cos C = `"adjacent side"/"hypotenuse" = "CD"/"AC" = 16/20 = 4/5`