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If cos θ = 2x1+x2\dfrac{2x}{1 + x^2}, find the values of sin θ and tan θ in terms of x.

find the values of sin θ and tan θ in terms of x. Trigonometrical Ratios, R.S. Aggarwal Mathematics Solutions ICSE Class 9.

Trigonometrical Ratios

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Answer

cos θ = basehypotenuse=2x1+x2\dfrac{\text{base}}{\text{hypotenuse}} = \dfrac{2x}{1 + x^2}

Let base = 2x and hypotenuse = 1 + x2

Now we will find perpendicular by using pythagoras theorem

Perpendicular2 = Hypotenuse2 - Base2

Perpendicular2 = (1 + x2)2 - (2x)2

Perpendicular2 = 1 + x4 + 2x2 - 4x2

Perpendicular2 = 1 + x4 - 2x2

Perpendicular2 = (x2 - 1)2

Perpendicular = (x2 - 1)

Now,

sin θ = perpendicularhypotenuse=x211+x2\dfrac{\text{perpendicular}}{\text{hypotenuse}} = \dfrac{x^2 - 1}{1 + x^2}

tan θ = perpendicularbase=x212x\dfrac{\text{perpendicular}}{\text {base}} = \dfrac{x^2 - 1}{2x}

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