Question

find Sin 18°/Cos 72°​

Answer 1

✤ To find:-

• $\sf \dfrac{sin \: 18 \degree}{cos \: 72 \degree}$

✤ Solution:-

We have ,

$\sf \dfrac{sin \: 18 \degree}{cos \: 72 \degree}$

By using trigonometric ratio's of complementary angle:

☆ cos (90°- θ) = cos θ

= $\sf \dfrac{cos\:(90\degree - 18\degree)}{cos \: 72 \degree}$

= $\sf \dfrac{cos \: 72 \degree}{cos \: 72 \degree}$

= $\sf 1$

Therefore,

$\sf \boxed{ \sf \dfrac{sin \: 18 \degree}{cos \: 72 \degree} = 1}$

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More complementary angles:-

• sin (90° - θ) = cos θ
• tan (90° - θ) = cot θ
• cot (90° - θ) = tan θ
• sec (90° - θ) = cosec θ
• cosec (90° - θ) = sec θ