Q8 of 186 Page 350

sec 70° sin 20° + cos 20° cosec 70° = ?

Consider (sec 70° sin 20°) + (cos 20° cosec 70°)

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

= (cosec 70° sin70°) + (cos 20° sec 20°)

= 1 + 1 (∵ cosec θ = 1/sin θ and sec θ = 1/cos θ )

= 2

sin 47° cos 43° + cos 47° sin 43° = ?

If sin 3A = cos (A – 10°) and ∠A is acute then ∠A = ?

If sec 4A = cosec (A – 10°) and 4A is acute then ∠A = ?