Question

cos54°等于多少分数

Answer 1

[√(10-2√5)]/4。cos54度=sin36°=√[(5-2√5)]/(3-√5)=√[(5-2√5)]*(3+√5)/[(3-√5)(3+√5)]=√{[(5-2√5)]*(3+√5)^2}/4=√[(5-2√5)*(14+2√5)]/4=[√(10-2√5)]/4。