The value of \(\displaystyle\prod^{{{10}}}_{\left\lbrace{r}={1}\right\rbrace}{\left({1}+{\tan{{r}}}^{\circ}\right)}\cdot\prod^{{{55}}}_{\left\lbrace{r}={46}\right\rbrace}{\left({1}+{\cot{{r}}}^{\circ}\right)}\) Attempt: \(\displaystyle\prod^{{{10}}}_{\left\lbrace{r}={1}\right\rbrace}{\left({1}+{\tan{{r}}}^{\circ}\right)}={\left({1}+{\tan{{1}}}^{\circ}\right)}{\left({1}+{\tan{{9}}}^{\circ}\right)}\cdots\cdots{\left({1}+{\tan{{4}}}^{\circ}\right)}{\left({1}+{\tan{{6}}}^{\circ}\right)}{{\tan{{5}}}^{\circ}}\) from

Malik Dean

Malik Dean

Answered question

2022-04-09

The value of {r=1}10(1+tanr){r=46}55(1+cotr)
Attempt: {r=1}10(1+tanr)=(1+tan1)(1+tan9)(1+tan4)(1+tan6)tan5 from tan(A+B)=tan10tanA+tanB1tanAtanB=tan10
could some help me to solve it

Answer & Explanation

Wrastirtyzp9w

Wrastirtyzp9w

Beginner2022-04-10Added 10 answers

{r=1}10(1+tanr){r=46}55(1+cotr)
{r=1}10(1+tanr){r=1}10(1+cot(45+r))
={r=1}10((1+tanr)(1+cot(45+r)))
={r=1}102
=210
The key observation is, both products have the same number of terms.
More details on how to simplify the middle term inside the product:
(1+tanr)(1+cot(45+r))
=(1+tanr)(1+1tan(45+r))
=(1+tanr)(1+1tan45×tanrtan45+tanr)
=(1+tanr)(1+1tanr1+tanr)
=(1+tanr)(21+tanr)
=2

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