# MATHS PPT.

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MATHS PROJECT BY CLASS 7-B GROUP MEMBER NAMES JASMEEN KAUR AHLUWALIA SANYA GUPTA KARAN PAL SINGH CHAHAL RAADHIKKA SEHGAL RAGHAV KHANNA PROPERTIES OF TRIANGLES

### TRIANGLES :

TRIANGLES A closed figure made up of 3 line segments is called a triangle. A triangle has three sides, three vertices and three angles.

### TYPES OF TRIANGLES :

TYPES OF TRIANGLES On the basis of sides: Equilateral triangle. Scalene triangle. Isosceles triangle. On the basis of angles: Acute angled triangle. Obtuse angled triangle. Right triangle.

### Classification of triangles on the basis of angles. :

Classification of triangles on the basis of angles. Acute angled triangle- A triangle each of whose angle measures less than 90 deg. is called an acute triangle. Right triangle- A triangle one of whose angles measure 90 deg. is called a right triangle. Obtuse triangle- A triangle one of whose angle measures more than 90 deg. is called an obtuse triangle.

### Classification of triangles on the basis of sides :

Classification of triangles on the basis of sides Equilateral triangle- A triangle having all sides equal is called an equilateral triangle. Isosceles triangle- A triangle having two sides equal is called an isosceles triangle. Scalene triangle- A triangle having all sides of different lengths is called a scalene triangle.

### Angle sum property of a triangle :

Angle sum property of a triangle In a triangle, the sum of 3 interior angles is 180 degrees.

### Triangle inequality :

Triangle inequality The sum of any two sides of a triangle, is greater than the third side.

Questions and answers Q1. In a ΔABC, if angle A= 72° and Angle B= 63°, find the measure of angle C. Ans. Angle C +72°+ 63°=180° ( Angle sum property) Angle C + 135°= 180°. Angle C= 180°- 135° Angle C= 45° Q2. In a ΔPQR, if angle Q= 105° and angle R= 40°, find the measure of angle P. Ans. Angle P + 105°+40°=180°. ( Angle sum property). Angle P + 145°= 180°. Angle P= 180°- 145°. Angle P= 35°.

Questions And Answers Q3. The two interior opposite angles of an exterior angle of a triangle are 60°and 80°. Find the measure of the exterior angle. Ans. Let the exterior angle be x. x= 60 +45 ( exterior angle property) x= 105°. Q4. An exterior angle of a triangle is of measure 70° and one of its interior opposite angles is of measure 25°. Find the measure of the other interior opposite angle. Ans. Let the other interior opposite angle be x. x= 70 – 25 x= 45°.

Questions and answers Q5. Two angles of a triangle are 30° and 80°. Find the measure of the third angle. Ans. Let the third side be x. x + 30°+ 80°= 180° x+ 110° = 180° x= 180°-110° x= 70°. Q6. One of the angles of a triangle is 80° and the other two angles are equal. Find the measure of the two angles. Let both the angles be x x+ x+ 80°= 180° (Angle sum property) 2x + 80°= 180°. 2x= 180°- 80°. 2x = 100°. x= 50°.

### General Questions :

General Questions Q1. Solve this equation: 5t + 28= 10 5t= 10- 28 5t = -18 t = -18/5 Q2. Solve: -4(2+ x)=8 -4X2 + (-4)Xx=8 -8 + (-4)x= 8 -8-4x = 8 -4x = 8+8 -4x= 16 x= -4

### General Questions :

General Questions Q3. Solve: 3( n-5)= 21 3n-3X5= 21 3n- 15= 21 3n =21+15 3n= 36 n= 12. Q4.Solve: 4 (2-x)= 8 8- 4x= 8 -4x= 8-8 -4x= 0

### Exterior angle property :

Exterior angle property In a triangle the exterior angle is equal to the sum of interior opposite angles.