Brahmagupta's Formula for the area of a cyclic quadrilateral: A = √[(s − a)(s − b)(s − c)(s − d)] where > a, b, c, d = lengths of the four sides > s = semiperimeter = (a + b + c + d)/2 Applies to any quadrilateral that can be inscribed in a circle (as shown in the diagram).

Confidence + consistency + discipline = @druski's formula for stardom in 2025. The jokes hit because the work behind the scenes never stops. ⁠ ⁠ The comedian and social superstar talks being one of pop culture’s biggest names, a collaboration he could do that would blow his parents’ minds and so much more in Billboard’s No. 1s issue:

Threadguy explains how YouTubers are completely taking over Hollywood "Hollywood’s formula for the last 50 years was that people only want familiar franchises like Disney and Star Wars. I strongly disagree. The proof is YouTube. People watch new creators, new streamers, new videos every day just because they're interesting" "The social feed killed the subscriber. You don't really subscribe to people anymore. You just see content on your feed that you want to watch" "I haven't seen a single ad for Obsession. I don't even watch horror movies, but I'm desperate to see it. It was made by a YouTuber for under $1 million"

Euler loved calculating prime numbers. He produced tables of all the primes up to 100,000 and even a few beyond. In 1732, he was also the first to show that Fermat’s formula for primes, 2^(2^n) + 1, breaks down when n = 5. Using new theoretical ideas, he managed to factor this ten-digit number into a product of two smaller numbers. One of his most curious discoveries was a formula that seemed to generate an unusually large number of primes. In 1772, he calculated all the values obtained by substituting the numbers from 0 to 39 into the formula x² + x + 41. He obtained the following list:

Unlock the power of geometry with these three fundamental theorems: > Pythagoras’ Theorem: The gold standard for right-angled triangles. Solve for any side using a² + b² = c². > Heron’s Formula: Find the area of any triangle using only its side lengths: no height required! Area = √[s(s−a)(s−b)(s−c)], where s = (a + b + c)/2 is the semi-perimeter. > Ceva’s Theorem: A deeper dive into triangle geometry. Three cevians AD, BE, and CF are concurrent if (BD/DC) × (CE/EA) × (AF/FB) = 1.

On this day, May 19 1681, Chinese mathematician and writer Mei Juecheng was born. He published Chishui yizhen (Pearls Recovered from the Red River), which included the infinite series expansion for sin(x), introduced to China via Jesuit missionaries. sin x = x − x³/3! + x⁵/5! − x⁷/7! + ⋯ (Originally from Gregory & Newton, introduced to China ~1701 as “Du Demei’s formula”)