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If vecxand vecy are two unit vectors and...

If `vecx`and `vecy` are two unit vectors and `theta` is the angle between them, then `1/2|vecx -vecy|` is equal to

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`(1/2|vecx-vecy|)^2=1/4(|vecx|^2+|vecy|^2-2|vecx|||vecy|costheta)`
`1/4(1+1-2*1*1costheta)`
`1/4(2-2costheta)`
`1/4*2(1-costheta)`
`1/2(2sin^2theta/2)`
`(1/2|vecx-vecy|)^2=sin^2theta/2`
`1/2|vecx-vecy|=|sintheta/2|`
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