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Is. - cosx=cosx

Answer» It is confusing for me.Why because,Sin(-x)= -sinx.Cos(-x)= cosx.But my math sir said .-Cosx is not equal to cosx.I want some clarification.
Yes because -cosx=cos(360-x)=cos x as it will lie in 4th quadrant and in 4th quadrant the value of cos is positive


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