Q53 of 93 Page 6

In the figure, AM ⊥ BC and AN is the bisector of ∠BAC. If ∠B = 70° and ∠C = 35°,  find  ∠MAN.

In the ΔABC, AN is the angle bisector of ∠BAC.
... ∠BAN = ∠NAC   ........    (i)
      Also ∠A + ∠B + ∠C = 180°
        ⇒ ∠A + 70° + 35° = 180°
⇒ ∠BAN + ∠NAC + 105° = 180°
⇒ 2 ∠BAN = 180° - 105° = 75°
                      ... Δ BAM = 37.5° 
In Δ ABM, we have ∠B + Δ BAM +Δ AMB = 180°
... 70° +∠BAM + 90° = 180°
                 ... ∠BAM = 20°  .......  (ii)
              Now ∠MAN = ∠BAN - ∠BAM = 37.5° - 20° = 17.5°

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