SOLUTION: how do you find the length of a leg of right triangle given hypotenuse and the angles?

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Question 726188: how do you find the length of a leg of right triangle given hypotenuse and the angles?

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
You use the trigonometric ratios
sin%28angle%29=opposite_leg%2Fhypotenuse
cos%28angle%29=adjacent_leg%2Fhypotenuse

For most angles, you would let your calculator figure out the values of the sine and cosine of that angle. Fifty to forty years ago, we used tables from books, or slide rules.

Sine and cosine of some angles can be calculated more easily.
A right triangle with acute angles measuring 30%5Eo and 60%5Eo is half of an equilateral triangle. If the length of the short leg (opposite the 30%5Eo angle) is a , the length of the hypotenuse will be 2a. and according the the Pythagorean theorem, the length of the other leg, b, will be
sqrt%28%282a%29%5E2-a%5E2%29=sqrt%283a%5E3%29=a%2Asqrt%283%29.

So, from the point of view of the 30%5Eo angle,
sin%2830%5Eo%29=a%2F2a=1%2F2 and cos%2830%5Eo%29=a%2Asqqrt%2F2a=sqrt%283%29%2F2 and
from the point of view of the 60%5Eo angle,
cos%2860%5Eo%29=a%2F2a=1%2F2 and sin%2860%5Eo%29=a%2Asqqrt%2F2a=sqrt%283%29%2F2
Ina any case, the legs of a right triangle with acute angles measuring 30%5Eo and 60%5Eo are as long as
1%2F2 and sqrt%283%29%2F2 times the length of the hypotenuse.

A right triangle with both acute angles measuring 45%5Eo is an isosceles right triangle. Its legs, being opposite angles with equal measure, have equal lengths. Such a triangle is half of a square, and the legs can be proven to be sqrt%282%29%2F2 times as long as the hypotenuse.
The Pythagorean theorem says that s%5E2%2Bs%5E2=c%5E2
Then s%5E2%2Bs%5E2=c%5E2 --> 2s%5E2=c%5E2 --> 4s%5E2=2s%5E2 --> sqrt%284s%5E2%29=sqrt%282c%5E2%29 --> 2s=c%2Asqrt%282%29 --> s=c%2A%28sqrt%282%29%2F2%29