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Find the incentre of a triangle formed b...

Find the incentre of a triangle formed by the lines `x "cos" (pi)/(9) + y "sin" (pi)/(9) = pi, x "cos" (8pi)/(9)+ y "sin" (8pi)/(9) = pi "` and `x "cos" (13pi)/(9) + y "sin" ((13pi)/(9)) = pi.`

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