PK - week 5 (4th lesson)
review the ideas from last week.
Exercises from HL book
- p.229 Q3a 3b
- Review Set 9A, Q1, 3, 5, 15
Intro to Sigma notation
triangular numbers
$1 \ 3 \ 6 \ 10 \ 15$
$1+2+3+4+5$
can be written as $$\sum_{i=1}^{5} i$$
The question now arises. How do we find the 100th triangular number?
recursive rule
T(n) = T(n-1) + n
explicit rule
Can we find T(n) without knowing T(n-1)???
T(n) = ???
using geometry
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