Introduction to :
Trigonometry, an in-depth study of triangles and functions, has many of its roots in algebra. As we mentioned, algebra sets the stage for a number of other mathematical branches, but perhaps none more so than trig. They’re pretty inseparable. They’re like Batman and Robin. Peanut butter and jelly. Super glue, chopsticks, and the palm of your hand. (What? You try separating them. We had to learn the hard way.)
We won’t get too far into trigonometric concepts with this guide, but it’s important to be aware as we take you through the massive overlap between the two. We combine algebra with geometry to find the third side of a triangle when we have the other two, and we can build on this concept with trigonometry to find and graph the ratios of the triangle’s sides. Any complex-looking equation you may come across in trigonometry—like ex + iy = ex(cos y + i sin y), for example—makes use of algebra. You can't just memorize this stuff, pass a test or two, and let baseball statistics push it out of your brain.
Lock away everything you’re about to learn, and keep the key in a safe place. You don’t want to have to hacksaw your way in later.