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Thought-Process to Discover Knowledge

Welcome to nubtrek.

Books and other education websites provide "matter-of-fact" knowledge. Instead, nubtrek provides a thought-process to discover knowledge.

In each of the topic, the outline of the thought-process, for that topic, is provided for learners and educators.

Read in the blogs more about the unique learning experience at nubtrek.
mathsConstruction / Practical Geometry (High)Construction of Triangles with Secondary Information

### Construction of Triangles using Angle, Side, Sum of 2 Sides

In this page, a short and to-the-point overview of constructing triangles with angle-side-sum of two sides is provided. Sum of two sides is a secondary parameter.

The reasoning on how to approach the problem and how the procedure works are provided.

click on the content to continue..

To construct a triangle, "side-angle-sum of other two sides" is provided. Which of the following is directly constructed using the given parameters?

• the triangle /_\ ABC
• the given angle with two line segments of given side and sum of sides
• the given angle with two line segments of given side and sum of sides

The answer is "the given angle with two line segments of given side and sum of sides"

To construct a triangle /_\ ABC with given "side-angle-sum of other two sides" bar(AB)=4cm, /_A=50^@, and bar(AC)+bar(BC) = 6cm. •  Construct a line and mark side bar(AB) with a compass measuring 4cm

•  measure 50^@ angle and draw a ray from point A

•  measure bar(AC)+bar(BC) =6cm in a compass and draw an arc cutting the ray at D

This is directly constructed from the given parameters.

With given "side-angle-sum of two sides" we constructed bar(AB), and bar(AD)=bar(AC)+bar(CB) at the given angle /_A. The objective now is to locate the point C in the line bar(AD).

Consider points p, q, r, s, and t on line bar(AD). Which of the following property is noted for points p and t in the line bar(AD)?

• bar(Ap)+ bar(pB) < bar(AD) as evident from the figure
• bar(At)+ bar(tB) > bar(AD) as evident from the figure
• both the above
• both the above

The answer is "both the above". It is noted that at a single position between the points A and D, the point C is located such that bar(AC)+bar(CB)=bar(AD).

With given "side-angle-sum of two sides" we constructed bar(AB), and bar(AD)=bar(AC)+bar(CB) at the given angle /_A.
The point C is visualized in bar(AD) such that bar(AC)+bar(CB)=bar(AD). Which of the following is an useful observation that will help to locate the point C along bar(AD)?

• the line segments bar(CD) and bar(CB) are equal
• the triangle /_\ BCD is isosceles
• both the above
• both the above

The answer is "both the above".

With given "side-angle-sum of two sides" we constructed bar(AB), and bar(AD)=bar(AC)+bar(CB) at the given angle /_A. The point C is visualized in bar(AD) such that bar(AC)+bar(CB)=bar(AD).

It is observed that /_\BCD is isosceles and only angle /_D and base bar(BD) are available. The position of point C is not yet marked. It is shown in the figure to visualize. Which of the following property help in identifying the point C?

• two angles of an isosceles triangles are equal. /_CDB = /_DBC
• a perpendicular bisector on the base of isosceles triangle passes through the third vertex
• both the above
• both the above

The answer is "both the above".

With given "side-angle-sum of two sides" we constructed bar(AB), and bar(AD)=bar(AC)+bar(CB) at the given angle /_A.

The point C is visualized in bar(AD) such that bar(AC)+bar(CB)=bar(AD).

It is observed that /_\BCD is isosceles and only angle /_D and base bar(BD) are available.

The position of point C is not yet marked. It is shown in figure to visualize. Using the property that
two angles of an isosceles triangles are equal. /_CDB = /_DBC
The angle /_CDB can be copied using a compass to mark line vec(BE). The point of intersection of vec(AD) and vec(BE) is the point C.
/_\ABC is constructed.

With given "side-angle-sum of two sides" we constructed bar(AB), and bar(AD)=bar(AC)+bar(CB) at the given angle /_A.

The point C is visualized in bar(AD) such that bar(AC)+bar(CB)=bar(AD).

It is observed that /_\BCD is isosceles and only angle /_D and base bar(BD) are available.

The position of point C is not yet marked. It is shown in figure to visualize. Using the property that
the perpendicular bisector on the base of isosceles triangle passes through the third vertex,
The line vec(MN) is drawn as bisector of bar(DB). The point of intersection of vec(AD) and vec(MN) is the point C.
/_\ABC is constructed.

Construction of Side-Angle-Sum of 2 Sides triangle : Visualize the point C and the /_\ BCD is isosceles triangle.

Locate point C by one of the following methods.

•  copy the angle

•  draw perpendicular bisector on the base.

slide-show version coming soon