Question

Answer only if you know don't give irrelevant answers if you don't know the answer then don't answer
$plaese \: answer \: fastly \: its \: an \: emergency$
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Answer 1

√3/2

Step-by-step explanation:

sinA = [√(3+√5) -√(5-√5) ]/4 = p /h

b =√( h^2 - p^2)

b = √(16 - [ (3 +√5 + (5- √5) - 2(√15-√15+√25-√25)]

= √(16 - 8 + 0) = √8 = 2√3

cosA = b/h = 2√3/4 = √3/2

Or you can find it by using trigonometric identity

cosA =√ (1 - sin^2A )

put value of sinA in this trigonometric identity& simplify further to get the answer.