Q12 of 186 Page 350

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

We are given that: cos (α + β) = 0

∴We can rewrite it as: cos (α + β) = cos (90° – 0°)

On comparing both sides, we get,

(α + β) = 0 = 90°

⇒ α = 90° – β

Therefore, sin (α – β) = sin (90° – β – β)

= sin (90° – 2β)

= cos 2β

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

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

sin (45° + θ) – cos (45° – θ) = ?

sec² 10° – cot² 80° = ?