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Mathematics

Evaluate the following :

sin222°+sin268°cos222°+cos268°\dfrac{\text{sin}^2 22° + \text{sin}^2 68°}{\text{cos}^2 22° + \text{cos}^2 68°} + sin2 63° + cos 63° sin 27°

Trigonometric Identities

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Answer

Since, angles are acute in the equation,

∴ cos(90° - θ) = sin θ, sin(90° - θ) = cos θ.

Using above equations in

sin222°+sin268°cos222°+cos268°\dfrac{\text{sin}^2 22° + \text{sin}^2 68°}{\text{cos}^2 22° + \text{cos}^2 68°} + sin2 63° + cos 63° sin 27°

= sin222°+sin2(9022)°cos222°+cos2(9022)°\dfrac{\text{sin}^2 22° + \text{sin}^2 (90 - 22)°}{\text{cos}^2 22° + \text{cos}^2 (90 - 22)°} + sin2 63° +cos 63° sin (90 - 63)°

= sin222°+cos222°cos222°+sin222°\dfrac{\text{sin}^2 22° + \text{cos}^2 22°}{\text{cos}^2 22° + \text{sin}^2 22°} + sin2 63° + cos 63° cos 63°

= 11\dfrac{1}{1} + sin2 63° + cos2 63°

= 1 + 1

= 2.

Hence, the value of expression is 2.

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