Answer:
Solution Given:
let ABC be an equilateral triangle with the vertex A(2,-1) and slope =-1.
and
∡ABC=∡BAC=∡ACB=60°
slope of BC![[ m_1]=-1](https://tex.z-dn.net/?f=%5B%20m_1%5D%3D-1)
we have
=60°
Slope of AB=![[ m_2]=a](https://tex.z-dn.net/?f=%5B%20m_2%5D%3Da)
now
we have
angle between two lines is

now substituting value
tan 60°= ± 
<u>doing criss-cross multiplication;</u>

=±(1+a)
<u>taking positive</u>


a=
<u>taking negative </u>


a=
Equation of a line when a =
and passing through (2,-1),we have

y+1=
(x-2)
y=
-1
<h3>

<u> is a first side equation of line.</u></h3><h3><u>again</u></h3>
Equation of a line when a =
and passing through (2,-1),we have

y+1=
(x-2)
y+1=
y=
<h3>

<u>is another equation of line.</u></h3>