D. 50
Step-by-step explanation:
a = 90° (angle subtended in semicircle)
a + c + 40° = 180° (by angle sum postulate of a triangle)
90° + c + 40° = 180°
c + 130° = 180°
c = 180° - 130°
c = 50°
12 is
13 is
Step-by-step explanation:
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