Question

cos 60 cos 30- sin60 sin 30=cos 90​

Answer 1

Answer:

Use sin(90

∘

−θ)=cosθ and cos(90

∘

−θ)=sinθ

and cos

2

θ+sin

2

θ=1

Now,

sin30

∘

⋅cos60

∘

+cos30

∘

⋅sin60

∘

=sin(90

∘

−60

∘

)⋅cos60

∘

+cos(90

∘

−60

∘

)⋅sin60

∘

=cos60

∘

⋅cos60

∘

+sin60

∘

⋅sin60

∘

=cos

2

60°+sin

2

60°=1

Answer 2

Answer:

cos =90

cos=1

sin =1

sin=2

cos=1