• In a right angled ΔOAB, where <BOA = θ,
    i. sinθ = \frac{Perpendicular}{Hypotenuse} = \frac{AB}{OB}

    ii. cosθ = \frac{Base}{Hypotenuse} = \frac{OA}{OB}

    iii. tanθ = \frac{Perpendicular}{Base} = \frac{AB}{OA}

    iv. cosecθ = \frac{1}{\sin \theta} = \frac{OB}{AB}

    v. secθ = \frac{1}{\cos\theta} = \frac{OB}{OA}

    vi. cotθ = \frac{1}{\tan\theta} = \frac{OA}{AB}

  • Trigonometrically Identities:
    Sin2θ + cos2θ = 1
    Sec2θ – tan2θ = 1
    Cosec2θ – cot2θ = 1

  • Angle of Elevation:
    Suppose a man from a point O looks up at an object P, placed above the
    level of his eye. Then, the angle which the line of sight makes with the
    horizontal line through O, is called the angle of elevation of P as seen
    from O. Angle of elevation of P from O = <AOP.

  • Angle of Depression:
    Suppose a man from a point O looks down at an object P, placed below
    the level of his eye, then the angle which the line
    of sight makes with the horizontal line through O,
    is called the angle of depression of P as seen from O.
Last modified: Friday, 8 May 2026, 7:16 AM