Two cars are moving on mutually perpendicular roads towards each other. The speed of the first car is 20 m / s

Two cars are moving on mutually perpendicular roads towards each other. The speed of the first car is 20 m / s, the speed of the second car is 30 m / s. Calculate the speed v12 of the first car in the frame of reference associated with the second.

moving towards each other
speed of the first = 20 m / s
speed of the second = 30 m / s
find the speed v 12
decision
2 cars are moving perpendicularly, so the speed triangle will be vector
the triangle is right-angled, then using the Pythagorean theorem we find V12
V12 = √ (v1 ^ 2 + v2 ^ 2) = √ (20 ^ 2 + 3 0 ^ 2) = √ (20 * 20 + 30) ^ 2 = √ (20 * 20 + 30 * 30) = √ (400 + 30 * 30) = √ (400 + 900) = √1300 = 36 m / s
answer: 36 m / s