A) \[\sin 36{}^\circ \]
B) \[\cos 36{}^\circ \]
C) \[\sin 7{}^\circ \]
D) \[\cos 7{}^\circ \]
Correct Answer: D
Solution :
The given expression is equal to |
\[(\sin 47{}^\circ +\sin 61{}^\circ )-(sin11{}^\circ +sin25{}^\circ )\]\[=2\sin 54{}^\circ \cos 7{}^\circ -2\sin 18{}^\circ \cos 7{}^\circ \]\[=2\cos 7{}^\circ \,(\sin 54{}^\circ -\sin 18{}^\circ )\] |
\[=2\,\cos 7{}^\circ \left[ \frac{\sqrt{5}+1}{4}-\frac{\sqrt{5}-1}{4} \right]=\cos 7{}^\circ \] |
You need to login to perform this action.
You will be redirected in
3 sec