Question 1166708
<pre>
{{{drawing(400,400,-3,3,-3,3,

graph(400,400,-3,3,-3,3),  

circle(0,2,.05), circle(-1,-1,.05), circle(1,-1,.05),
triangle(0,2,-1,-1,1,-1) )}}}

You did not specify whether the rotation is counter-clockwise or clockwise,
so since 45° is positive, I'll assume it is a counter-clockwise rotation.

The formulas are

x' = x∙cos(θ) - y∙sin(θ)
y' = x∙sin(θ) + y∙cos(θ)

I'll let you do all the substitutions.  Here's how the new triangle looks,
(in green).

{{{drawing(400,400,-3,3,-3,3,

graph(400,400,-3,3,-3,3),  

green(circle(-sqrt(2),sqrt(2),.05), circle(0,-sqrt(2),.05), circle(sqrt(2),0,.05),
triangle(-sqrt(2),sqrt(2),0,-sqrt(2),sqrt(2),0)),


circle(0,2,.05), circle(-1,-1,.05), circle(1,-1,.05),
triangle(0,2,-1,-1,1,-1) )}}}  

Edwin</pre>