Evalute the following: sin 20°/ cos 70°

(i) We have,

= \( \dfrac{sin (90° – 70°)}{ cos 70°} =\dfrac{ cos 70°}{cos70° }=1\) [∵ sin (90 – θ) = cos θ]

(ii) We have,

= \(\dfrac{ cos (90° – 71°)}{ sin 71°} = \dfrac{sin 71°}{ sin 71°}\) = 1 [∵ cos (90 – θ) = sin θ]

(iii) We have,

\( \dfrac{sin 21°}{ cos 69°} = \dfrac{sin (90° – 69°)}{ cos 69°} = \dfrac{cos 69°}{ cos69°}\) = 1 [∵ sin (90 – θ) = cos θ]

(iv) We have,

\( = \dfrac{tan (90° – 10°) }{ cot 80° }= \dfrac{cot 80°}{ cos80°}\) = 1 [∵ tan (90 – θ) = cot θ]

(v) We have,

 =\(\dfrac{ sec (90° – 79°)}{ cosec 79°} = \dfrac{cosec 79°}{ cosec 79°}\) = 1

[∵ sec (90 – θ) = cosec θ]