Properties of Triangles 3 Question 4

4. Which of the following pieces of data does not uniquely determine an acute angled ABC ( R being the radius of the circumcircle)?

(2002, 1M)

(a) a,sinA,sinB

(b) a,b,c

(c) a,sinB,R

(d) a,sinA,R

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Answer:

Correct Answer: 4. (d)

Solution:

  1. First solve each option separately.

(a) If a,sinA,sinB are given, then we can determine b=asinAsinB,c=asinAsinC. So, all the three sides are unique.

So, option (a) is incorrect.

(b) The three sides can uniquely make an acute angled triangle. So, option (b) is incorrect.

(c) If a,sinB,R are given, then we can determine b=2RsinB,sinA=asinBb. So, sinC can be determined.

Hence, side c can also be uniquely determined.

(d) If a,sinA,R are given, then

bsinB=csinC=2R

But this could not determine the exact values of b and c.



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