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If A,B,C,D are the angles of quadrilater...

If A,B,C,D are the angles of quadrilateral, then find `(sum tan A)/(sum cot A).`

A

cot A cot B cot C cot D

B

tan A tan B tan C tan D

C

`-tan A tan B tan C tan D`

D

`-cot A cot B cot C cot D`

Text Solution

Verified by Experts

The correct Answer is:
B
`A+B+C+D=2pi`
`therefore A+B=2pi-(C+D)`
`therefore tan(A+B)=tan [2pi - C+D)]=-tan(C+D)`
`rArr (tan A + tan B)/(1-tan A tan B)=-(tan C + tan D)/(1-tan C tan D)`
`rArr (tan A+ tan B)(1-tan C tan D)`
`=-(1-tan A tan B)(tan C+tan D)`
`rArr tan A+tan B-tan A tan C tan D?-tan B tan C tan D`
`=-[(tan C+tan D-tan A tan B tan C-tan A tan B tan D)]`
`rArr tan A + tan B+ tan C+tan D`
`= tan A tan B tan C + tan A tan C tan D+ tan A tan D + tan B tan C tan D`
Dividing both sides by tan A tan B tan C tan D, we get
`(tan A+ tan B + tan C + tan D)/(ta A tan B tan C tan D)`
`=(1)/(tan D)+(1)/(tan D)+(1)/(tan C)+(1)/(tan A)`
`= cot D + cot B + cot C + cot A`
`rArr (tan A +tan B + tan C + tan D)/(cot A + cot B + cot C + cot D) = tan A tan B tan C tan D`
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