Răspuns :
18)
E = sin(arccos(3/5)+arccos(4/5))
arccos(3/5)+arccos(4/5) =
= arccos((3/5)•(4/5) - √(1-9/25)√(1-16/25)) =
= arccos((12/25 - 4/5•3/5)) = arccos(0) = pi/2
E = sin(arccos(0)) = √(1-0²) = 1
18)
E = sin(arccos(3/5)+arccos(4/5))
arccos(3/5)+arccos(4/5) =
= arccos((3/5)•(4/5) - √(1-9/25)√(1-16/25)) =
= arccos((12/25 - 4/5•3/5)) = arccos(0) = pi/2
E = sin(arccos(0)) = √(1-0²) = 1