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A room is 12m long, 9m wide and 8m high. Find the cosine ...

A room is 12m long, 9m wide and 8m high. Find the cosine of the angle which a diagonal of the room makes with the floor of the room.

A.

1517

B.

917

C.

815

D.

1217

Correct answer is A

Given length of the room = 12m; breadth = 9m and height = 8m.

The room is a cuboid in shape, therefore the length of the diagonal = l2+b2+h2

= 122+92+82

=289

= 17m.

The diagonal makes an angle with the diagonal of the floor: 122+92

= 225

= 15m

The cosine of the angle that the diagonal makes with the floor (θ) = 1517.