Question

If cos 20°-sin 20º = p then cos 40° is equal to
(a) -p√2-p²
(b) p√2-p²
(c) p+V2-p?
(d) none of these

no scam....step by step explanation pls​

Answer 1

Answer:

b) p√2-p²

Step-by-step explanation:

cos 20 - sin 20=p

squaring on both sides

cos²20 + sin²20 -2sin20cos20 =p²

=> 2Sin20Cos20 = 1 - p²

=> Sin40 = 1 - p²

Cos40 =√1-sin²40 =  √(2p²-p⁴) = p√2-p²