Question

ii) sec 70°sin 20° + cos 20°cosec 70° = 2​

Answer 1

Answer:

We have,

sec 70° sin 20° + cos 20° cosec 70°

= sec (90° - 20°) sin 20° + cos 20° cosec (90° - 20°)

= cosec20° sin20° + cos20° sec20° [∵∵Sec(90°-A)=CosecA & Cosec(90° - A) = SecA ]

=sin20∘sin20∘+cos20∘cos20∘=sin⁡20∘sin⁡20∘+cos⁡20∘cos⁡20∘. [∵∵Cosec A=(1/SinA) & SecA =(1/CosA) ]

= 1 + 1 = 2