Correct answer = (d) 2
(1st method:)
We have
sec70° sin 20°+ cos 20° cosec 70°
= 1 + 1
= 2
(2nd method:)
sec70° sin 20°+ cos 20° cosec 70°
= cosec(90° − 70°) sin 20° + cos 20° sec(90° − 70°)
= cosec 20° sin 20° + cos 20° sec 20°
= 1/sin 20° × sin 20° + cos 20° × 1/cos 20°
= 1 + 1
= 2
