In ∆DEF shown below, points A, B, and C are taken on DE, DF and EF respectively such that EC = AC and CF = BC. If ∠D = 40°, then what is ∠ACB in degrees?
Explanation:
At point C,
(180° − 2x) + z + (180° − 2y) = 180°
z = 2x + 2y − 180° = 2(x + y) − 180° ...(i)
Also, in ΔDEF, x + y + 40° = 180°
x + y = 140°
Substituting in equation (i), we get,
z = 2 × 140 − 180 = 100°
Hence, option (c).
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