
56 Make: Robotic Arms
Our main goal is to solve for C, which is really our original Ө
2
variable.
Knowing that our goal is to eventually find this value, from the three law-of-
cosines equations, we want to select the one that uses the C variable. This
gives us the following starting point:
c = a + b -2ab cos(C)
Though this is a good place to start, we’re trying to solve for uppercase C, not
our lowercase c variable as it’s written here, so let’s rearrange our equation
once more, this time solving for C. We can accomplish this by subtracting
a and b from both sides of the equation, then dividing both sides of the
equation by –2ab, now allo ...