{"id":8386,"date":"2021-11-21T00:41:38","date_gmt":"2021-11-20T19:11:38","guid":{"rendered":"https:\/\/mathemerize.com\/?p=8386"},"modified":"2021-11-21T01:13:02","modified_gmt":"2021-11-20T19:43:02","slug":"what-is-wallis-formula-in-integration","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/what-is-wallis-formula-in-integration\/","title":{"rendered":"What is walli’s formula in integration ?"},"content":{"rendered":"
If m,n \\(\\in\\) N & m, n \\(\\ge\\) 2, then<\/p>\n
\n(a) \\(\\int_{0}^{\\pi\/2}\\) \\(sin^nx\\)dx = \\(\\int_{0}^{\\pi\/2}\\) \\(cos^nx\\)dx = \\((n-1)(n-3)….(1 or 2)\\over {n(n-2)….(1 or 2)}\\) K<\/p>\n
where K = \\(\\begin{cases} \\pi\/2 & \\text{if n is even}\\ \\\\ 1 & \\text{if n is odd}\\ \\end{cases}\\)<\/p>\n
(b) \\(sin^nx.cos^mx\\)dx = \\([(n-1)(n-3)….(1 or 2)][(m-1)(m-3)….(1 or 2)]\\over {(m+n)(m+n-2)(m+n-4)….(1 or 2)}\\) K<\/p>\n
where K = \\(\\begin{cases} \\pi\/2 & \\text{if both m and n are even}\\ \\\\ 1 & \\text{otherwise}\\ \\end{cases}\\).<\/p>\n<\/blockquote>\n
Example<\/strong><\/span> : Evaluate : \\(\\int_{-\\pi\/2}^{\\pi\/2}\\) \\(sin^4x cos^6x\\)dx<\/p>\n
Solution<\/strong><\/span> : We have,<\/p>\n
I = \\(\\int_{-\\pi\/2}^{\\pi\/2}\\) \\(sin^4x cos^6x\\)dx = 2 \\(\\int_{0}^{\\pi\/2}\\) \\(sin^4x cos^6x\\)dx <\/p>\n
I = 2\\((3.1)(5.3.1)\\over 10.8.6.4.2\\) \\(\\pi\\over 2\\) = \\(3\\pi\\over 6\\)<\/p>\n\n\n