Tick the correct answer and justify: In ∆ABC,  The angle B i

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221. In the given Fig, O is a point in the interior of a triangle ABC, OD ⊥ BC,OE ⊥ AC and OF ⊥ AB. Show that
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(ii) AF2 + BD2 + CE2 = AE2 + CD2 + BF2.


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230. Tick the correct answer and justify: In ∆ABC, AB equals 6 square root of 3 space cm comma space AC space equals space 12 space cm space and space BC space equals space 6 space cm. The angle B is:
(A) 120°                (B) 60°
(C) 90°                  (D) 45°



AB squared equals left parenthesis 6 square root of 3 right parenthesis squared space equals space 108
AC squared equals left parenthesis 12 right parenthesis squared space equals space 144
BC squared space equals space left parenthesis 6 right parenthesis squared space equals space 36

Now,  
         AB squared plus BC squared space equals space 108 plus 36
rightwards double arrow space space space space space space space space space space space space space space space space space space space space equals space 144 space equals AC squared
∴ ∆ABC is a right angle triangle right angled at B.
Hence, the correct answer is (c) = 90°.

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