{"id":9222,"date":"2022-01-03T17:46:54","date_gmt":"2022-01-03T12:16:54","guid":{"rendered":"https:\/\/mathemerize.com\/?p=9222"},"modified":"2022-01-03T19:12:52","modified_gmt":"2022-01-03T13:42:52","slug":"what-is-the-formula-of-cosa-b","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/what-is-the-formula-of-cosa-b\/","title":{"rendered":"What is the Formula of Cos(A + B) ?"},"content":{"rendered":"
In this post you will learn what is the formula for cos (A + B) with examples.<\/p>\n
The formula of cos(A + B)<\/strong> is cos A cos B – sin A sin B<\/strong>.<\/p><\/blockquote>\n
Example<\/span><\/strong> : If sin A = \\(3\\over 5\\) and cos B = \\(9\\over 41\\), find the value of cos (A + B).<\/p>\n
Solution<\/span><\/strong> : We have,<\/p>\n
sin A = \\(3\\over 5\\) and cos B = \\(9\\over 41\\)<\/p>\n
\\(\\therefore\\) cos A = \\(\\sqrt{1 – sin^2 A}\\) and sin B = \\(\\sqrt{1 – cos^2 B}\\)<\/p>\n
\\(\\implies\\) cos A = \\(\\sqrt{1 – {9\\over 25}}\\) = \\(4\\over 5\\) and sin B = \\(\\sqrt{1 – {81\\over 1681}}\\) = \\(40\\over 41\\)<\/p>\n
Now, By using above formula,<\/p>\n
cos (A + B) = cos A cos B – sin A sin B<\/p>\n
= \\(4\\over 5\\) \\(\\times\\) \\(9\\over 41\\) – \\(3\\over 5\\) \\(\\times\\) \\(40\\over 41\\) = \\(-84\\over 205\\)<\/p>\n
Example<\/span><\/strong> : Find the value of cos 75.<\/p>\n
Solution<\/span><\/strong> : cos 75 = cos (45 + 30)<\/p>\n
By using above formula,<\/p>\n
cos (45 + 30) = cos 45 cos 30 – sin 45 sin 30<\/p>\n
\\(\\implies\\) cos 75 = \\(1\\over \\sqrt{2}\\) \\(\\times\\) \\(\\sqrt{3}\\over 2\\) – \\(1\\over \\sqrt{2}\\) \\(\\times\\) \\(1\\over 2\\)<\/p>\n
\\(\\implies\\) cos 75 = \\(\\sqrt{3} – 1\\over 2\\sqrt{2}\\)<\/p>\n","protected":false},"excerpt":{"rendered":"
In this post you will learn what is the formula for cos (A + B) with examples. Cos (A + B) Formula : The formula of cos(A + B) is cos A cos B – sin A sin B. Example : If sin A = \\(3\\over 5\\) and cos B = \\(9\\over 41\\), find the …<\/p>\n