No.
Triangles have three angles and three sides. A quadrilateral has four angles and four sides.
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an isosceles trapeziod could be a quadrilateral because it has 4 sides and a quadrilateral has 4 sides
isosceles triangle
Are isosceles triangle sometimes an equilateral triangle
An isosceles triangle with its apex cut off by a line parallel to the base.
An obtuse triangle is not necessarily isosceles, but it can be.