KVPY Sample Paper KVPY Stream-SX Model Paper-21

\[\sin 47{}^\circ +\sin 61{}^\circ -\sin 11{}^\circ -\sin 25{}^\circ \] is equal to

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

\[(\sin 47{}^\circ +\sin 61{}^\circ )-(sin11{}^\circ +sin25{}^\circ )\]\[=2\sin 54{}^\circ \cos 7{}^\circ -2\sin 18{}^\circ \cos 7{}^\circ \]\[=2\cos 7{}^\circ \,(\sin 54{}^\circ -\sin 18{}^\circ )\]

\[=2\,\cos 7{}^\circ \left[ \frac{\sqrt{5}+1}{4}-\frac{\sqrt{5}-1}{4} \right]=\cos 7{}^\circ \]

Report Error

KVPY Sample Paper KVPY Stream-SX Model Paper-21

question_answer \[\sin 47{}^\circ +\sin 61{}^\circ -\sin 11{}^\circ -\sin 25{}^\circ \] is equal to A) \[\sin 36{}^\circ \] B) \[\cos 36{}^\circ \] C) \[\sin 7{}^\circ \] D) \[\cos 7{}^\circ \]

\[\sin 47{}^\circ +\sin 61{}^\circ -\sin 11{}^\circ -\sin 25{}^\circ \] is equal to

A) \[\sin 36{}^\circ \]

B) \[\cos 36{}^\circ \]

C) \[\sin 7{}^\circ \]

D) \[\cos 7{}^\circ \]