The formula for the nth triangular number is $T_n = \frac{n(n+1)}{2}$. Use the formula to find the 8th triangular number.
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Step 1: Substitute n = 8 into the formula. Show more…
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Steven C.
3. The sum of the first n natural numbers is sometimes called the n-th triangular number Tn. Triangular numbers are so-named because one can represent them with triangular shaped arrangements of dots. The first several triangular numbers are 1, 3, 6, 10, 15, et cetera. Determine a formula for the sum of the first n triangular numbers and prove it using PMI.
Adi S.
The formula for the sum of the first n natural numbers is n(n + 1)/2.
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