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UPPSC AE Civil 2013 Official Paper II

Option 2 : three angle conditions and one side condition

**Triangulation: **It is the method of surveying based on the trigonometric proposition that if one side and two angles of a triangle are known, the remaining sides can be computed.

A triangulation system consists of a series of joined or overlapping triangles in which an occasional side is measured and remaining sides are calculated from angles measured at the vertices of the triangles.

**Interpretation:**

As triangle consists of maximum three angles, the requirement of four angle measurement is just unnecessary and hence option 1 and 3 is eliminated.

For plotting a triangle accurately, even if all three angles are given, the triangle cannot be plotted without at least data of any one side of the triangle.

**∴**** Along with three angles, for centered triangle we requires at least one side length and hence three angle conditions and one side condition is necessary as the equation of condition for centered triangle. **