To find the distance AB across a river, a surveyor laid off a distance BC=363m on one side of the river. It is found that B=111∘20′ and C=13∘15′. Find AB.
Q. To find the distance AB across a river, a surveyor laid off a distance BC=363m on one side of the river. It is found that B=111∘20′ and C=13∘15′. Find AB.
Convert Angles to Decimal Degrees: Convert angles B and C from degrees and minutes to decimal degrees for easier calculations. Angle B=111 degrees 20 minutes =111+6020=111.333 degrees.Angle C=13 degrees 15 minutes =13+6015=13.25 degrees.
Calculate Angle A: Use the angle sum property of a triangle, where the sum of angles in a triangle is 180 degrees. Calculate angle A.Angle A = 180−(Angle B+Angle C)=180−(111.333+13.25)=55.417 degrees.
Apply Law of Sines for AB: Apply the Law of Sines to find AB: (sinA/AB)=(sinB/BC). Rearrange to find AB: AB=BC×(sinA/sinB).
Calculate sinA and sinB: Calculate sinA and sinB using a calculator:sinA=sin(55.417)≈0.829,sinB=sin(111.333)≈0.932.
Substitute Values for AB: Substitute values into the formula: AB=363×(0.829/0.932)≈363×0.889≈322.917 meters.
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