Question

If sin^2 5 theta = sin 5 theta , then find the value of theta ( 0 < theta < 90 )?

Answer 1

Sin^2 5Ф  =  Sin5Ф
Sin^2 5Ф - Sin5Ф = 0
Sin5Ф(Sin5Ф - 1) = 0
Sin5Ф = 0
Sin5Ф = Sin0
5Ф = 0
Ф = 0
or 
sin5Ф - 1 = 0
sin5Ф = Sin90
Ф = 18
so answer is Ф = 18          (0<Ф<90)