If O be the origin and if the co-ordinates of any two points #P_1# and #P_2# be respectively #(x_1,y_1) ,(x_2,y_2)#, prove that #OP_1 * OP_2 cosP_1OP_2 = x_1x_2 + y_1y_2#?
1 Answer
Nov 21, 2017
Coordinates of points
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