Question

cos18/sin 72,Evaluate it.

Answer 1

cos18/sin72

cos(90-72)/sin72

sin72/sin72

1

Answer 2

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$= \frac{cos \: 18 {}^{0} }{sin \: 72 {}^{0} }$

$sin(90 {}^{0} - \theta) = cos \: \theta$

$= \frac{cos \: 18 {}^{0} }{sin(90 {}^{0} - \theta)}$

$= \frac{cos \: 18 {}^{0} }{sin(90 {}^{0} - 18 {}^{0}) }$

$= \frac{cos \: 18 {}^{0} }{cos \: 18 {}^{0} }$

$= 1$