What is the value of c?

units?

You may recognize that ∆WYZ is a 3-4-5 right triangle. Without any work, then
  c = 5


If you don't remember that a right triangle with legs 3 and 4 has a hypotenuse of 5, you can compute it using the Pythagorean theorem.
  c² = 3² + 4²
  c² = 9 + 16 = 25
  c = √25 = 5

c ≈ 5

using Pythagoras's theorem,

c² = a² + b²

c² = 4² + 3²

c² = 16 + 9

c = √25

c = 5

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