the series 1 + 1\/2 + 1\/4 + 1\/8 + …. converges to 2. here, the area of the big rectangle (2 square units) is equal to the sum of areas of each square.<\/figcaption><\/figure>\na series that can’t make up its mind<\/h3>\n finally, let’s take a look at a series that diverges due to the fact that the sum never stabilizes.<\/p>\n
<\/p>\n
now, it’s tempting to say that the series converges to 0. but in reality, the sequence of partial sums oscillates between 1 and 0 forever. <\/p>\n
<\/p>\n
because the partial sums never reach a definite limit, we say that this series diverges.<\/p>\n
(by the way, this is another example in which the terms an<\/sub><\/em> do not approach zero as n<\/em> → ∞. that fact alone automatically implies that the series diverges!)<\/p>\nget out your telescopes<\/h3>\n most of the time, it is very difficult to find a formula for the partial sums of a given series. however, in one important case, the partial sums seem to “collapse” like the sections of a telescope. in that case, it will be very easy to decide whether the series converges or diverges and to find its sum.<\/p>\nsmall telescopes used to be made to collapse for easy storage. the multiple sections of the telescope could slide into each other.<\/figcaption><\/figure>\na telescoping series<\/strong> is one whose terms cancel with one another in a certain way.<\/p>\nfor example, consider the following series.<\/p>\n
<\/p>\n
let’s write out the first four partial sums.<\/p>\n
<\/p>\n
i’ve highlighted the cancelling terms in red and blue. once you cancel out those middle terms, there will only be two terms remaining in the partial sum, the first term 1\/1 = 1, and the last term.<\/p>\n
let’s see how this plays out in general.<\/p>\n
<\/p>\n
now we can actually find the sum series, based on the general formula for the partial sums!<\/p>\n
<\/p>\n
after all of the cancellations, this telescoping series collapses down to converge on the value 1.<\/p>\n
summary<\/h2>\n now that we’ve gone over the series fundamentals, let’s recap.<\/p>\n
\na series<\/strong> is the sum of a sequence.<\/li>\nseries can be expressed as a sum of (infinitely many) terms or by using sigma notation<\/strong>.\n \n<\/li>\n
the k<\/em>th partial sum<\/strong> of a series is the sum of its first k<\/em> terms.<\/li>\na series converges to a sum s<\/em> if and only if the sequence of its partial sums converges to s<\/em>.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"a series is the sum of a sequence of numbers. we’ll review the series fundamentals and give a few example problems from the ap calculus bc exam.<\/p>\n","protected":false},"author":223,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[240],"tags":[241],"ppma_author":[24932],"class_list":["post-10709","post","type-post","status-publish","format-standard","hentry","category-ap","tag-ap-calculus"],"acf":[],"yoast_head":"\n
ap calculus bc review: series fundamentals - magoosh blog | high school<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n