Question

Express the following as sum or difference of trigonometric ratios
a) 2 sin 60. sin66° b) 2 sin 32º. cos 28° c) 2 cos 78°. sin 42°
d) 2 cos 54º. sin 66°​

Answer 1

Answer:

sin78

∘

−sin66

∘

−sin42

∘

+sin6

∘

=(sin78

∘

−sin42

∘

)+(sin6

∘

−sin66

∘

)

=2sin18cos60+2sin(−30)cos36

=sin18−cos36

=

4

5

−1

−

4

5

+1

=−

2

1