• # question_answer The value of $\mathbf{tan}{{\mathbf{4}}^{o}}.\mathbf{tan4}{{\mathbf{3}}^{o}}.\mathbf{tan4}{{\mathbf{7}}^{o}}.\mathbf{tan8}{{\mathbf{6}}^{o}}$is A)  2                                B)  3              C)  1 D)  4

(c): $tan{{4}^{{}^\circ }}.tan{{43}^{{}^\circ }}.tan{{47}^{{}^\circ }}.tan{{86}^{{}^\circ }}$ $=tan{{4}^{{}^\circ }}.tan{{43}^{{}^\circ }}.tan({{90}^{{}^\circ }}-{{43}^{{}^\circ }}).tan({{99}^{{}^\circ }}-{{4}^{{}^\circ }})$ $=tan{{4}^{{}^\circ }}\times tan{{43}^{{}^\circ }}\times cot{{43}^{{}^\circ }}\times cot{{4}^{{}^\circ }}=1$ $\left[ tan\left( {{99}^{{}^\circ }}-\theta \right)=cot\theta ;tan\theta .cot\theta =1 \right]$