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In a triangle ABC, if the angle c is obtuse, then tanAtanB= 1)>1 2) 3)=1 4)=0

In a triangle ABC, if the angle c is obtuse, then tanAtanB=
1)>1
2)
3)=1
4)=0

Grade:11

1 Answers

Arun
25750 Points
5 years ago
Dear Sunny
 
 

In case that C is obtuse,

 

Then C>90.

So A+B msut be less than 90... (because in a triangle A+B+C=180, and C is above 90)

So tan(A+B) must be postivie... (Since A+B is acute

tan(A+B) = (tanA+tanB)/(1-tanAtanB)

So 1-tanAtanB>0..... (Only then tan(A+B) can be positive)

Hence tanAtanB

 

Hope it helps

 

Regards

Arun (askIITians forum expert)

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