1.

If x+y=z, then cos^(2)x+cos^(2)y+cos^(2)z-2cosx.cosy.coszis equal to

Answer»

`COS^(2)Z`
`SIN^(2)z`
0
1

Solution :`cos^(2)x+cos^(2)y+cos^(2)z-cosz(cos(x+y)+cos(x-y))`
`=cos^(2)x+cos^(2)y+cos^(2)z-cos^(2)z-cos(x+y).cos(x-y)=1`


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