Trigonometric EquationHard
Question
Which of the following numbers is rational ?
Options
A.sin 15o
B.cos 15o
C.sin 15o cos 15o
D.sin 15o cos 75o
Solution
Since, sin 15o 
and cos 15o
and sin 15o cos 75o
= sin 15o.sin15o
Therefore, all these values are irrational and
= sin 15o. cos15o
2 sin 15o. cos15o
sin 30o = 
which is rational.
and cos 15o
and sin 15o cos 75o
= sin 15o.sin15o
Therefore, all these values are irrational and
= sin 15o. cos15o
2 sin 15o. cos15o sin 30o = which is rational.Create a free account to view solution
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