2sin^2(x/2) == sin(x)tan(x/2)
I can't get this and I have test coming up. Can anyone help me?
I can't get this and I have test coming up. Can anyone help me?
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2 sin²(x/2)
= 2 sin(x/2) sin(x/2)
= 2 sin(x/2) cos(x/2) sin(x/2) / cos(x/2)
= (2 sin(x/2) cos(x/2)) * (sin(x/2) / cos(x/2))
= sin(x) tan(x/2)
= 2 sin(x/2) sin(x/2)
= 2 sin(x/2) cos(x/2) sin(x/2) / cos(x/2)
= (2 sin(x/2) cos(x/2)) * (sin(x/2) / cos(x/2))
= sin(x) tan(x/2)
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Given:
2sin²(x/2) = sin(x)tan(x/2)
Use tan(u) = sin(u)/cos(u):
2sin²(x/2) = sin(x)sin(x/2)/cos(x/2)
Remove common factor:
2sin(x/2) = sin(x)/cos(x/2)
2sin(x/2)cos(x/2) = sin(x)
let 2u = x, then x/2 = u:
sin(2u) = 2sin(u)cos(u)
sin(2u) = sin(2u)
QED
2sin²(x/2) = sin(x)tan(x/2)
Use tan(u) = sin(u)/cos(u):
2sin²(x/2) = sin(x)sin(x/2)/cos(x/2)
Remove common factor:
2sin(x/2) = sin(x)/cos(x/2)
2sin(x/2)cos(x/2) = sin(x)
let 2u = x, then x/2 = u:
sin(2u) = 2sin(u)cos(u)
sin(2u) = sin(2u)
QED