What is always true about the angles of an isosceles triangle?

all three angles are congruent.
at least two of the angles are congruent.
the vertex angle is a right angle.
the vertex angle is obtuse.

we know that

An isosceles triangle has two equal sides and two equal angles

so

case A) All three angles are congruent

The statement is false

Because, only two angles are congruent

case B) At least two of the angles are congruent

The statement is true

An isosceles triangle has two congruent angles  

case C) The vertex angle is a right angle

The statement is false

Because, the vertex angle sometimes is a right angle but not always

case D) The vertex angle is obtuse

The statement is false

Because, the vertex angle sometimes is a obtuse angle but not always

δabc ≅ δdcb by sas because

db ≅ ac . . given (side)

bc ≅ bc . . reflexive property (side)

∠dbc ≅ ∠ acb . . alternate interior angles where transversal bc crosses parallel lines bd and ac (included angle)

differentiate (x^14(x^-2)^4with respect to the variable

the parentheses don't balance in your input.

differentiate 0 with respect to

the final answer is

0

hope this