# Approximating integrals

Some integrals just can’t get calculated. For example, there is no explicit formula for the integral of the photo. But what if we must know its value or the rocket won’t launch? Well, as every engineer knows, when you can’t be precise you approximate. There are many ways to do that, but we describe here five of them (three in this post and the later two in future posts). The left point Riemann sum, the right point Riemann sum, the midpoint rule, the trapezoid rule and the Simpson rule.

# Calculating pi using a probabilistic method

In probability theory, each discrete random variable X has a Probability Mass Function (PMF) from which we can extract the probability of every possible outcome of X. In addition, there is a function called mean (or expectation) E[X], which give as the outcome we should expect from the random variable X. We exploit this attribute in order to (approximately) calculate pi.

# The prisoner’s dilemma

Three prisoners know that one of them is going to be executed. Agony overcame one of them (prisoner A) and he begged the guard to tell him who of them is the unlucky. After some thinking, the guard decides to reveal someone, other than him, who’s not gonna perish.

He now regrets for asking, because, previously, he had a 2/3 chance to stay intact but now only 1/2. Is his deduction correct?

# Open Circuit Time Constants

Besides Miller’s Theorem, there is another technique we can use to determine the 3db frequency of an amplifier. It is known as Open Circuit Time Constants method and it is just as powerful and useful as Miller’s counterpart.

# What is the probability of four people taking one ace?

Let’s say we shuffle a deck and share it to four players (13 cards are given to each player). What is the probability that everyone gets an ace? Click on “Continue reading” to reveal the solution.