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  1. In an acute–angled triangle ABC if sin (B + C – A) =
    3
    and tan (C + A – B) = 1, then C is equal to
    2

    1. 37.5°
    2. 67.5°
    3. 52.5°
    4. 72.5°
Correct Option: C

As per the given question ,

Sin (B + C – A) =
3
= sin 60°
2

⇒ B + C – A = 60° ..... (i)
Again,
tan (C + A – B) = 1 = tan 45°
⇒ C + A – B = 45° ..... (ii)
On adding (i) and (ii) , we get
∴ B + C – A + C + A – B = 60° + 45°
⇒ 2C = 105°
⇒ C =
105°
= 52.5°
2



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