If it's a right angle triangle and an acute angle plus the length of a leg is given then use trigonometry to find the hypotenuse.
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The square of the hypotenuse minus the square of the leg you know will give you the square of the unknown leg.
To solve a 30-60-90 triangle, you need to know the length of one side. The hypotenuse is twice as long as the shortest leg (the side opposite the 30 angle) The longer leg (opposite the 60 angle) is the length of the shorter leg times the square root of 3. So in summary: If you know the hypotenuse, divide it by 2 to find the shorter leg, and multiply that times the square root of 3 to find the longer leg. If you know the longer leg, divide it by the square root of 3 to find the shorter leg, then multiply that by 2 to find the hypotenuse. If you know the shorter leg, multiply it by 2 to find the hypotenuse. Multiply the shorter leg length by the square root of 3 to find the longer leg.
The hypotenuse is the square root of (82 +152) = 17.
If two right triangles have (hypotenuse and a leg of one) = (hypotenuse and the corresponding leg of the other) then the triangles are congruent.
"Hypotenuse-leg" is not necessarily the right-triangle version of "side-angle-side". It's the right-triangle version of "side-side-side", because if you know that it's a right triangle, and you know the hypotenuse and a leg, then you can calculate the length of the other leg. If you want to work with "side-angle-side", and you know the hypotenuse and a leg, then you can find the angle between them, because it's the angle whose cosine is (the known leg) divided by (the hypotenuse), and you can look it up.