Multiple Choice: In the triangle at right, x must be:Homework Help ✎
none of these
The triangle is isosceles meaning 2 sides are equal.
The measure of x must be the same as the other unknown angle because base angles are equal in an isosceles triangle.
Since the sum of all the interior angles of a triangle must be 180°, then x + x + 42° = 180°.
So the answer is (b).