src/Maths/Geometry/Triangle.php
public function isIsoceles()
    {
        return (bool) (
            $this->isEquilateral()==false && (
                ($this->getSegmentAB()->getLength() == $this->getSegmentBC()->getLength()) ||
                ($this->getSegmentAB()->getLength() == $this->getSegmentCA()->getLength()) ||
                ($this->getSegmentBC()->getLength() == $this->getSegmentCA()->getLength())
            )
        );
    }
public function isIsoceles()
    {
        return (bool) (
            $this->isEquilateral()==false && (
                ($this->getSegmentAB()->getLength() == $this->getSegmentBC()->getLength()) ||
                ($this->getSegmentAB()->getLength() == $this->getSegmentCA()->getLength()) ||
                ($this->getSegmentBC()->getLength() == $this->getSegmentCA()->getLength())
            )
        );
    }
Test if a triangle is equilateral : [AB] = [BC] OR [AB] = [CA] OR [BC] = [CA]

@return  bool