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

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.

817

C.

815

D.

1217

Correct answer is A

ABCD is the floor. By pathagoras 

AC2 = 144 + 81 = 225 

AC = 15cm

Height of room 8m, diagonal of floor is 15m

Therefore, the cosine of the angle which a diagonal of the room makes with the floor is 

EC2 = 152 + 82 cosine

adjHyp=1517 

EC2 = 225+64

EC = 289

= 17