Question

evaluate :
1) sin 18° ÷ cos 72°​

Answer 1

Given

$\huge \rm \frac{sin18 {}^{ \circ} }{ {cos72}^{ \circ} }$

We know,

• sinθ = cos(90° - θ)
• cosθ = sin(90° - θ)

Using above Formulae,

$\large \bf \frac{ {sin18}^{ \circ} }{ {cos72}^{ \circ} } = \frac{cos(90 - 18)}{{cos72}^{ \circ}} \\ \\ \rm\implies \cancel{\frac{cos72 \degree}{cos72 \degree} } \: \: \: \: = \orange1$