(cos kx) 10- - If Lim x-+0 I where ...
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(cos kx) 10- - If Lim x-+0 I where a and b are co-prime, then the value of (a+b), is 2 + (1) 365 (2) 375 (3) 387 (4) 400

JEE/Engineering Exams
Maths
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[ begin{array}{l} frac{1-cos x}{x^{2}}+frac{1-cos 2 x}{x^{2}}+frac{1-cos 3 x}{x^{2}}+cdots frac{1-cos 10 x}{x^{2}} Rightarrow frac{1}{2}+frac{4}{2}+frac{9}{2}+frac{16}{2}+frac{25}{2}+frac{36}{2}+frac{49}{2}+frac{64}{2}+frac{81}{2}+frac{100}{2} end{array} ] ( =frac{1}{2} sum_{n=1}^{10} n^{3} quadleft[begin{array}{c}4(-cos n=1 n^{2}end{array}right) ) ( =frac{1}{2} cdot frac{n(n+1)(2 n+1)}{6} ) solved by ( =frac{1}{1242}+8 times 11 times 217=frac{385}{2}=frac{9}{b} ) an lilliom sine il 2 rateng ( therefore a+b=387 )
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