Mathematics - Properties of Triangle Question with Solution | TestHub
MathematicsProperties of Triangler1,r–R formula basedMedium2 minQB
MathematicsMediumsingle choice
In triangle ABC, A-B=120° and R=8r. Find cos C.
Options:
Answer:
C
Solution:
Let t=sin(C/2). Since A+B=180°-C, 2sin(A/2)sin(B/2)=cos((A-B)/2)-cos((A+B)/2)=1/2-t . Then r/R=4sin(A/2)sin(B/2)t=2t(1/2-t)=1/8, giving (4t-1)²=0 and t=1/4. Hence cos C=1-=7/8.
Stream:JEESubject:MathematicsTopic:Properties of TriangleSubtopic:r1,r–R formula based
⏱ 2mℹ️ Source: QB
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