Delta (r)

By: Daniel Bise

One of the items someone was confused about was “delta”. Delta is the capital of the fourth letter of the Greek alphabet. However, it has a completely unrelated purpose in mathematics.

In math, delta (r) represents “change in…” and is used in many formulas. One example is the slope formula. Slope can be stated as rise/ run or ry/ rx. This means, to find slope, you take the difference of the y values and divide it by the difference in the x values.

Another use of delta in a formula is the velocity formula. Velocity is the change in displacement divided by the change in time, or rd/rt.

Sample problem:

You are traveling at 50 mph, and then accelerate to 70 mph. This acceleration takes 7 seconds. You want to know what the average change in velocity is. So you subtract 50 from 70 to get 20 mph (which is your change in displacement, rd), and subtract 0 from 7 to get 7 seconds (which is the change in time, rt) then divide 20 by 7 to get 2.857 mph/sec. This is the average change in velocity for the given period of acceleration.

So, when you are writing a formula and you want to express the difference of two values of the same variable you can use delta and then the variable (example: rx).