Q10 of 186 Page 350

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

We are given that: sec 4A = cosec (A – 10°)

∴We can rewrite it as: cosec (90° – 4A) = cosec (A – 10°)

On comparing both sides, we get,

90° – 4A = A – 10 °

⇒ A + 4A = 90° + 10°

⇒ 5A = 100°

⇒ A = 20°

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

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

If A and B are acute angles such that sin A = cos B then (A + B) = ?

If cos (α + β) = 0 then sin (α – β) = ?