CLASS 10B MATHS : TRIGNOMETRICAL IDENTITIES

We started the Chapter on trigonometrical identities today.

We began to understand and the learn the trigonometrical ratios of sin, cos, tan, cosec, sec and cot in relation to a right-angled triangle.

We learnt that trigonometrical identities are equations showing the relationships between various trigonometrical ratios.

Right Angled Triangle

A right-angled triangle (the right angle is shown by the little box in the corner) has names for each side:

• Adjacent is adjacent to the angle "θ",
• Opposite is opposite the angle, and
• the longest side is the Hypotenuse.

• "Sine, Cosine and Tangent"

  The three most common functions in trigonometry are Sine, Cosine and Tangent. We will use them a lot!
  They are simply one side of a triangle divided by another.
  For any angle "θ":

  Sine Function: sin(θ) = Opposite / Hypotenuse Cosine Function: cos(θ) = Adjacent / Hypotenuse Tangent Function: tan(θ) = Opposite / Adjacent

  Other Functions (Cotangent, Secant, Cosecant)

  Similar to Sine, Cosine and Tangent, there are three other trigonometric functions which are made by dividing one side by another:

  Cosecant Function: csc(θ) = Hypotenuse / Opposite Secant Function: sec(θ) = Hypotenuse / Adjacent Cotangent Function: cot(θ) = Adjacent / Opposite

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• Now do Ex.23(A) Nos.1, 2 and 3