Q.
If the equation ax2+2bx+3c=0 and 3x2+8x+15=0 have a common root, where a,band c are the lengths of the sides of a△ABC, then sin2A+sin2B+sin2C is equal to
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a
1
b
32
c
2
d
2
answer is D.
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Detailed Solution
Discriminant o{ the equation 3x2+8x+15=0 is given byD=64−180=−116<0so it , roots are imaginary and therefore roots are conjugate to each other. Therefore, one common root means both the roots are common.∴ a3=2b8=3c15⇒ a3=b4=c5=k (say), k≠0Now, a2 + b2 = c2⇒ΔABC isrightangled. ∴ sin2A+sin2B=sin2C⇒sin2A+sin2B+sin2C=2sin2C=2sin290∘=2
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