Consider the given expression
cosθsin(90∘+θ)+sin(−θ)sin(180∘+θ)+tan(90∘+θ)cotθ
We know that
sin(90∘+θ)=cosθ
sin(−θ)=−sinθ
sin(180∘+θ)=−sinθ
tan(90∘+θ)=−cotθ
Therefore,
=cosθcosθ+−sinθ−sinθ−cotθcotθ
=1+1−1
=1
Hence, the value is 1.
Prove that:
(i) sin θ cos (90∘−θ)+sin(90∘−θ)cos θ=1
(ii) sin θcos (90∘−θ)+cos θsin (90∘−θ)=2
(iii) sin θ cos(90∘−θ)cos θsin (90∘−θ)+cos θ sin (90∘−θ)sin θcos (90∘−θ)=1
(iv) cos(90∘−θ)sec(90∘−θ)tan θcosec(90∘−θ)sin(90∘−θ)cot(90∘−θ)+tan(90∘−θ)cot θ=2
(v) cos(90∘−θ)1+sin(90∘−θ)+1+sin(90∘−θ)cos(90∘−θ)=2cosec θ
(vi) sec(90∘−θ)cosec θ−tan(90∘−θ)cot θ+cos225∘+cos265∘3 tan 27∘ tan 63∘=23
(vii) cot θ tan(90∘−θ)−sec(90∘−θ)cosec θ+√3 tan 12∘ tan 60∘ tan 78∘=2