Divide through when non-zero by the numerator and denominator,
OK, after help from here, I tried 4 more questions and thought i got the hang of this. Now i have another dilemma. :S
By expressing: tan(alpha + beta) = sin(alpha + beta) / cos(alpha + beta)
Prove that: tan(alpha + beta) = tan alpha + tan beta / 1 - tan alpha tan beta
Here are my first steps:
= sin(alpha + beta) / cos(alpha + beta)
= sin alpha cos beta + cos alpha sin beta / cos alpha cos beta - sin alpha sin beta
now im stuck,
should i cancel out the cos and sin from top and bottom?
i tried that, but that didn't work. after i thought, since i was lookin for tan in my answer, i would sin / cos = tan
that also did not work out.... (or maybe i did something wrong)
please guide me.
Thus, you are going to get some canceling.
And you also need to use the fact that,
I am not saying if the cosines are not zero you can divide through, thus the formula for tangent addition will hold true.what do you mean by "Divide through when non-zero"