How to use this applet:
Simply click the "next step" button to advance to the next stage of the explanation. When you have reached the last stage, the button changes to "Restart". Click "Restart" to go back to the beginning of the explanation.Notes on the maths used in the applet:
Any triangle can be divided into 2 smaller triangles by drawing a line perpendicular to a side through the opposite angle.
Look at each of these 2 smaller triangles seperately.
Sin = opposite/hypotenuse
In the right triangle sinB = h/a
Therefore h = asinB
In the left triangle sinA = h/b
Therefore h = bsinA
Since h is the same in both equations, the 2 equations are equal to each other.
aSinB = bSinA
Divide both sides by sinAsinB.
asinB/(sinAsinB) = bsinA/(sinAsinB)
a/sinA = b/sinB
It may be proven in the same manner that b/sinB = c/sinC
Therefore a/sinA = b/sinB = c/sinC
Other useful information:
See also
* Cosine Rule
* Applications of Trigonometry using the Sine Rule
