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# Calculating 2 sides of right triangle if you only know the hypotenuse and angle?

Posted on 2006-07-12
Medium Priority
2,331 Views
I need a formula in the form of

side1 = ...
side 2 = ...

Assume hypotenuse is 5 and anle is 30 degreess

I know the formula is sin(side1/hypotenuse) = 30 ... but I forgot how to extract the side1
0
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Accepted Solution

ozo earned 2000 total points
ID: 17092628
the sides are 5*sin(30°), and 5*cos(30°)
0

LVL 69

Expert Comment

ID: 17092631
>I know the formula is sin(side1/hypotenuse) = 30 ... but I forgot how to extract the side1

The arcsin function reverses the sin function:
side1/hypotenuse = arcsin(30)
side1 = hypotenuse * arcsin(30)

For side2, it's cos:
cos(side2/hypotenuse) = 30
side2/hypotenuse = arccos(30)
side2 = hypotenuse * arccos(30)
0

LVL 69

Expert Comment

ID: 17092650
Oops, ozo has it right.  The correct formula is side1/hypotenuse = sin(30).
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Author Comment

ID: 17092724
Why isn't it:

Side 1 = hypotenuse * sin(angle)
Side 2 = hypotenuse * cos(angle)
0

LVL 39

Expert Comment

ID: 17092756
that is exactly what ozo said, but using the numbers you gave
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LVL 69

Expert Comment

ID: 17092759
That's what ozo wrote - the hypotenuse is 5, right?
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Author Comment

ID: 17093062
its not giving me the same results as this site:

http://www.1728.com/trig.htm
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