Progression (Sequence and Series)Hard

Question

In a triangle the lengths of the two larger sides are 10 and 9, respectively. If the angles are in AP, then the length of the third side can be

Options

A.
B.3√3
C.5
D.None of these

Solution

      
Since, angles of a triangle are in AP.
⇒     α + (α - δ) + (α + δ) = 180o
⇒         α = 60o
Using cosine law in ᐃABC,
cos 60o =
⇒      
⇒       x2 = 91
⇒       x =

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