Question

sin? 15º+sin75°/
Cos 36° + cos54°​

Answer 1

Answer:

Explanation:

we can also write in this way

sin15+sin75 (numerator part)

apply sinA+sinB fomula

sinA+sinB=2sin(A+B/2)cos(A-B/2)

let A=15 and B=75

2sin(15+75/2)cos(15-75/2)

2sin(90/2)cos(60/2)   cos(-a)=cosa

2sin45cos30

2*1/root2*root3/2

root(2/3) equation 1

we know the value of cos 36= root5+1/2

cos 54= root(10-2root5)/4

cos 36+cos54

root5+1/2 + root(10-2root5)/4

4root2/3/2root5+root(10-2roo5)+2 equation 2

divide 1and 2 equation

we will get the final answer as 2root5+root(10-2root5)+2/4