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∠ BAC = 80°

Step-by-step explanation:

The sum of the interior angles of quadrilateral ACDB = 360°

DB and DC are tangents to the circle, thus

∠ DBA = ∠ ACD = 90° ( angle between tangent/ circle at point of contact )

Thus

∠ BAC + 90° + 90° + 100° = 360°

∠ BAC + 280° = 360° ( subtract 280° from both sides )

∠ BAC = 80°

option (b) is correct

step-by-step explanation:

to find the solution of this system, we need to convert it into reduced row-echelon form. we have,

after applying row operations r2 -> r2/2 and r3 -> r3/3, we get,