In Fig. 6.44, the side QR of ∠PQR is produced to a point S. If the bisectors of ∠PQR and ∠PRS meet at point T, then prove that
∠ZQTR = ∠ZQPR.
Answers
Bisector of ∠PQR and ∠PRS meet at point T
In ΔQTR, ∠TRS is an exterior angle.
∠QTR + ∠TQR = ∠TRS
∠QTR = ∠TRS − ∠TQR (1)
For ΔPQR, ∠PRS is an external angle.
∠QPR + ∠PQR = ∠PRS
∠QPR + 2∠TQR = 2∠TRS (As QT and RT are angle bisectors)
∠QPR = 2(∠TRS − ∠TQR)
∠QPR = 2∠QTR [By using equation (1)]
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All necessary formulas⤵️
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Angle sum property of triangle states that the sum of interior angles of a triangle is 180°. Proof .Thus, the sum of the interior angles of a triangle is 180°.
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Alternate interior angles are angles formed when two parallel or non-parallel lines are intersected by a transversal.Alternate interior angles are equal if the lines intersected by the transversal are parallel.
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The sum of 2 numbers
example
how to find "a" if a is not mentioned
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The sum of two numbers
example
how to find "a" if a is not mentioned
Given
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If there is a common ray between and so it is a adjacent angle.
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Vertical angles are pair angles formed when two lines intersect. Vertical angles are sometimes referred to as vertically opposite angles because the angles are opposite to each other.
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Here 180°.
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Given࿐
Bisector of ∠PQR and ∠PRS meet at point T
∠QTR=
2
1
∠QPR
In ΔQTR, ∠TRS is an exterior angle.
∠QTR + ∠TQR = ∠TRS
∠QTR = ∠TRS − ∠TQR (1)
For ΔPQR, ∠PRS is an external angle.
∠QPR + ∠PQR = ∠PRS
∠QPR + 2∠TQR = 2∠TRS (As QT and RT are angle bisectors)
∠QPR = 2(∠TRS − ∠TQR)
∠QPR = 2∠QTR [By using equation (1)]
∠QTR=∠QPR\red{\boxed{\tt{∠QTR = ∠QPR}}}
∠QTR=∠QPR
All necessary formulas
Angle sum property
Angle sum property of triangle states that the sum of interior angles of a triangle is 180°. Proof .Thus, the sum of the interior angles of a triangle is 180°.
Example:−
a+b+c=180°\red{\boxed{a+b+c=180°}}
a+b+c=180°
Alternate interior angle
Alternate interior angles are angles formed when two parallel or non-parallel lines are intersected by a transversal.Alternate interior angles are equal if the lines intersected by the transversal are parallel.
complementary angle
The sum of 2 numbers=90°=90°=90°
example
how to find "a" if a is not mentioned
Given
a=?a= \: ?a=?
b=40b = 40b=40
a+40=90°a+40=\:90°a+40=90°
a=90−40°a=90-40°a=90−40°
a=50°a=50°a=50°
supplementary angle
The sum of two numbers=180°= \:180°=180°
example a+b=180°a+b=180°a+b=180°
how to find "a" if a is not mentioned
Given
a=?a= \:?a=?
b=40b =\: 40b=40
a+40=180°a+40=180°a+40=180°
a=180−40°a=180-40°a=180−40°
a=140°a=140°a=140°
Adjacent angle
If there is a common ray between ∠a{\bf∠}a∠a and ∠b{\bf∠}b∠b so it is a adjacent angel
Vertical opposite angle
Vertical angles are pair angles formed when two lines intersect. Vertical angles are sometimes referred to as vertically opposite angles because the angles are opposite to each other.
lenear pair of angles
⋆
Here ∠a{\bf∠}a∠a +∠b+{\bf∠}b+∠b === 180°.