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in a triangle the cosines of two angles are inversely proportional to the sides opposite to the corresponding angled then the triangle is? 1)isoceles 2)right-angled 3)equilateral 4)none of these. please give the reason for the answer too.

in a triangle the cosines of two angles are inversely proportional to the sides opposite to the corresponding angled then the triangle is?
1)isoceles
2)right-angled
3)equilateral
4)none of these.
please give the reason for the answer too.

Grade:12

2 Answers

Saurabh Koranglekar
askIITians Faculty 10335 Points
4 years ago
576-1878_1.PNG
Vikas TU
14149 Points
3 years ago
Dear student 
acosA=bcosB⇒2RsinAcosA=2RsinBcosB
⇒sin2A=sin2B
A=B
or 2A+2B=180 
A+B=90 
C=90 
So the triangle is right angled triangle and it may be an isosceles triangle as well (90-45-45)
Good Luck 

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