if cos25⁰ + sin25⁰ =p, then cos50⁰ is

(A) ∫ 2-p² (b) – ∫ 2-9² © p ∫ 2-p² (d) – p ∫ 2-p²

this symbol represent ∫ square root . pl. show the working

Dear student

Cos25 + Sin25 = K .........1 
Cos2Q = Cos^2Q - Sin^Q 
=> (CosQ+SinQ)(CosQ-SinQ)
Square equation 1 
Cos^25 +Sin^2 25 + 2Cos25*Sin25 = K^2
1+ sin80 = k^2
Sin 80 = k^2 -1 
Draw traingle and apply pythagorus theorem 
Cos 50 = ksqrt(2-k^2)