Find the length of the third side. If necessary, round to the nearest tenth.
12

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Work Shown:
a = 9, b = 12 are the two legs of the right triangle
c = unknown is the hypotenuse
Apply the pythagorean theorem to find c
a^2 + b^2 = c^2
9^2 + 12^2 = c^2
81 + 144 = c^2
225 = c^2
c^2 = 225
c = sqrt(225)
c = 15
Answer:
15
Step-by-step explanation:
Since this is a right angled triangle we can use pythagoras theorem to work out the length of the hypotenuse, or the the longest side.
pythagoras theorem says that a²+b²=c² with c² being the hypotenuse, or missing side here.
12²+9²=225
Because 225 is equal to C², or C squared, we must take the square root in order to find the actual length.
√225 = 15