How do you determine if two lines are perpendicular?

What can be said about the relationship between triangles and circles? check all that apply. a) many circles can be inscribed in a given triangle b) exactly one triangle can be inscribed in a given circle c) exactly one circle can be inscribed in a given triangle d) many triangular shapes can be circumscribed about a given circle

In trapezoid efgh, m∠hef=(4x2+16)∘ and m∠gfe=(5x2+12)∘. find the value of x so that efgh is isosceles.

Which of the following is true for the relation f(x)=2x^2+1