A) \[\frac{47}{40}\]
B) \[\frac{59}{40}\]
C) \[\frac{51}{40}\]
D) \[\frac{41}{40}\]
Correct Answer: D
Solution :
| [d]\[\cos ec\,A-\cot A=\frac{4}{5}\] ...(1) |
| Also \[\cos e{{c}^{2}}A-{{\cot }^{2}}A=1\] |
| \[\Rightarrow \,\,\,\,(\cos ec\,\,A-\cot A)\,\,(\cos ec\,A+\cot A)=1\] |
| \[\Rightarrow \,\,\,\frac{4}{5}\,(\cos ec\,\,A+\cot A)\,=1\] |
| \[\Rightarrow \,\,\,\cos ec\,\,A+\cot A\,=\frac{5}{4}\] .(2) |
| From eqs. (1) and (2). we get \[\cos ec\,\,A\,=\frac{41}{40}\] |
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