The number of integral values of k, for which the equation 7 cosx+5sinx=2k+1 has a solution, is
A
4
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B
8
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C
10
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D
12
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Solution
The correct option is B 8 −√72+52≤(7cosx+5sinx)≤√72+52 So, for solution −√74≤(2k+1)≤√74 or −8.6≤(2k+1)≤8.6or−9.6≤2k≤7.6 or −4.8≤k≤3.8, So, integral values of k are -4, -3, -2, -1, 0, 1, 2, 3 (eight values)