Question

In the given figure, AD is perpendicular to BC. Find: 5 cos x

Answer 1

ΔADB is a right-angled triangle.
∴ AB²
= AB² + BD²
= 12² + 16²
= 144 + 256
= 400
⇒ AB = 20cm
ΔADC is a right-angled triangle.
∴ AC²
= AD² + DC²
= 12² + 9²
= 144 + 81
= 225
⇒ AC = 15cm
5 cos x 

= `5 xx "BD"/"AB"`

= `5 xx (16)/(20)`
= 4.