In triangle abc , angle a is a right angle and angle b = 45. if ab = 19 feet, what is bc?

If angle A measure 90° and angle B is 45° , that leaves 45° for angle C.  (90 + 45 + 45 = 180)
If both non right angles are 45° we have an isosceles right triangle and AC is also 19 feet.

So now we can use the Pythagorean theorem to find the missing side.

a² + b² = c²  and we are looking for BC - the hypotenuse of the triangle

19² +19² = c²   361+361 = c²   722= c² and c=√722 or about  26.87

Line the mark up so you will find your answer