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Linear Equations In Two Variables

Question
CBSEENMA9001999

In figure, ∆ABC and ∆ABD are equilateral triangles. Find the coordinates of points C and D.


Solution

∵ ∆ABC is an equilateral triangle
∴AC = BC = AB
⇒ BC = AB
⇒ BC = 2a
In right triangle COB,
OB2 + OC2 = BC
rightwards double arrow space space a2 + OC= (2a)2
rightwards double arrow  OC2 + 3a2
rightwards double arrow  OC space equals space square root of 3 space straight a
therefore space space space space space space space space space space straight C rightwards arrow space space left parenthesis 0 comma space square root of 3 space straight a right parenthesis
Similarly,   straight D space rightwards arrow space left parenthesis 0 comma space minus square root of 3 space straight a right parenthesis