Expert: Steve Holleran - 4/16/2008

Question
hello i have a triange that angle a is 90 angle b is 15 and angle c is i dont know what but i dont need to know the angles also side a-b is 800 how would i figure out side b-c and side a-c actually please just explain and tell me because i need a answer soon sorry picture is not good sorry no pic

Answer
Hi Daniel,

This is a right-triangle trig problem, so we're going to use the sine, cosine and tangent functions.

In your diagram, call the hypotenuse of the triangle x and the side across from angle B y.  

Then you can use the following:

        cos 15 = adjacent / hypotenuse = 800 / x

so       x = 800 / cos 15 = 828.22

For y, you can use :

        tan 15 = opposite / adjacent = y / 800

so       y = 800 * tan 15 = 214.36.

I don't know if you use this, but the trig functions on a right triangle can be remembered easily using :


                      SOH CAH TOA

Sin = opp/hyp,   cos = adj/hyp   tan = opp/ady


Hope you get this in time.

Steve