সংযুক্ত ও যৌগিক কোণের ত্রিকোণমিতিক অনুপাত
tanθ tan3θ tan5θ tan7θ tan9θ tan11θ tan13θ=? θ=π/28
−2-2−2
12\frac{1}{2}21
−1-1−1
111
: দেওয়া আছে, θ=π28⇒π2=14θ \theta=\frac{\pi}{28} \Rightarrow \frac{\pi}{2}=14 \theta θ=28π⇒2π=14θtanθtan3θtan5θtan7θ \tan \theta \tan 3 \theta \tan 5 \theta \tan 7 \theta tanθtan3θtan5θtan7θ
tan9θtan11θtan13θ=tanθtan3θtan5θtan7θtan(14θ−5θ)tan(14θ−3θ)tan(14θ−θ)=1tanθtan3θtan5θtanπ4tan(π2−5θ)tan(π2−3θ)tan(π2−θ)=1⋅tanθtan3θtan5θ⋅1⋅tan5θ⋅tan3θ⋅tanθ=1 \begin{array}{l} \tan 9 \theta \tan 11 \theta \tan 13 \theta \\ =\tan \theta \tan 3 \theta \tan 5 \theta \tan 7 \theta \\ \tan (14 \theta-5 \theta) \tan (14 \theta-3 \theta) \\ \tan (14 \theta-\theta) \\ =\frac{1}{\tan \theta \tan 3 \theta \tan 5 \theta} \tan \frac{\pi}{4} \\ \tan \left(\frac{\pi}{2}-5 \theta\right) \tan \left(\frac{\pi}{2}-3 \theta\right) \tan \left(\frac{\pi}{2}-\theta\right) \\ =\frac{1 \cdot}{\tan \theta \tan 3 \theta \tan 5 \theta} \cdot 1 \cdot \tan 5 \theta \cdot \tan 3 \theta \cdot \tan \theta \\ =1 \end{array} tan9θtan11θtan13θ=tanθtan3θtan5θtan7θtan(14θ−5θ)tan(14θ−3θ)tan(14θ−θ)=tanθtan3θtan5θ1tan4πtan(2π−5θ)tan(2π−3θ)tan(2π−θ)=tanθtan3θtan5θ1⋅⋅1⋅tan5θ⋅tan3θ⋅tanθ=1
Answer: ঘ
প্রমাণ কর যে, sin75∘+sin15∘sin75∘−sin15∘=3 \frac{\sin 75^{\circ}+\sin 15^{\circ}}{\sin 75^{\circ}-\sin 15^{\circ}}=\sqrt{3} sin75∘−sin15∘sin75∘+sin15∘=3.
যদি tanθ=x \tan \theta=x tanθ=x হয়, তবে sin2θ \sin 2 \theta sin2θ এর মান কত?
s=a+b+c2 \mathrm{s}=\frac{\mathrm{a}+\mathrm{b}+\mathrm{c}}{2} s=2a+b+c এবং
Δ=ABC \Delta=A B C Δ=ABC ত্রিভুজের ক্ষেত্রফল।
যদি α+β+γ=0 \alpha+\beta+\gamma=0 α+β+γ=0 হয় তবে, প্রমাণ কর যে, , cosα+cosβ+cosγ \cos \alpha+\cos \beta+\cos \gamma cosα+cosβ+cosγ
=4cosα2cosβ2cosγ2−1 =4 \cos \frac{\alpha}{2} \cos \frac{\beta}{2} \cos \frac{\gamma}{2}-1 =4cos2αcos2βcos2γ−1