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‘STRAIGHT LINES, Points to be remembered :, , 1) Distance between two points ( x1, yi) &(x2,y2) is V (x2 — x1)’ + (y2yy, , 2) Centroid of a triangle having vertices (x1, y1) «( 2,2) &( x3,y3) is., (Cxrets)3 (yrtyztys/3), , 3) Incentre of a triangle is given by ( (axr+ bxx+ exs)(a + b+ c) , (ayr+, , byzt eys\la + b+ 6), , , , 4) Equation of a line having slope ‘m’ & Y- intercept ‘c’ is given by, yemx+e, , 5) Equation of a line passing through a given point (x1, y1) & having, slope ‘m’ is given by y—y, = m(x—xi), , 6) Equation of a line passing through two given points (x1, y1) &( x2,Y2), is given by y—yi = (x—mi), , , , y2-yl x2—x1, , 7) Equation of a line making intercepts ‘a’ & “b” from the co-ordinate, axis is given by wa + y/b=1, , 8) Equation of a line in normal form is given by x cosa + y sina =p, 9) Angle between two lines having slopes ‘m,’ & ‘m,” is given by, Tan® = (m,—m,)/ (1 +m,.m,), , a) Two lines will be parallel if m, =m & perpendicular, , , , if mm 1