Final Cover - For Printing

triangle AB θC ABC,^ ∠B = 90^0. Therefore^ ∠A +^ ∠C = 90^0. Let^ ∠A = 30^0 , therefore sin 30^0

= ⎜⎛⎝^12 ⎞⎠⎟. Since^ ∠A +^ ∠B = 90^0 ,^ ∠B = 60^0. Therefore sin (90^0 – 30^0 ) = sin 60^0 which is

hypotenuse

opposite

AC

BC⎟=

⎠

⎜ ⎞

⎝

⎛ , which is cos 30 (^0) in which case BC becomes the adjacent side and AC is
the hypotenuse. This logic may be applied to other trigonometic ratios too.

4. Line of sight
   An imaginary line which is formed when a person is looking at an object without
   either looking up or down is said to be the line of sight or line of vision.


5. Angle of elevation
   When an object above the line of sight is to be seen, the line of sight which is raised
   by an angle from the horizontal level is known as the angle of elevation.


6. Angle of depression
   When an object below the line of sight is to be seen, the line of sight which is lowered
   by an angle from the horizontal level is known as the angle of depression.

All the three concepts - line of sight, angle of elevation and the angle of depression

may be taught by an embossed diagram depicting the nature of the three.

ΣNx^2 - ⎜⎝⎛NΣx⎠⎞^2 ⎟