Page 179 - Start Up Mathematics_7

8. In a right-angled triangle, the side opposite to the right angle is known as the hypotenuse and
the other two sides are called its legs.

9. Pythagoras theorem: In a right-angled triangle, the square of the hypotenuse is equal to the
sum of the squares of the other two sides. Conversely, if the square of any one side is equal
to the sum of squares of the other two sides, then the angle opposite the greatest side is a right
angle.
Review Exercises

Multiple ChoiCe Questions

1. A triangle whose angles measure 40°, 40° and 100° is:
(a) scalene (b) right (c) isosceles (d) equilateral
2. In a scalene triangle, if from the same vertex a median and an altitude is drawn to the opposite
side, then the measure of:
(a) median < altitude (b) median > altitude (c) median = altitude (d) 2 median = altitude

3. The sum of any two sides of a triangle is:
(a) less than the third side (b) equal to the third side
(c) greater than the third side (d) any of (a), (b), (c) depending on the triangle

4. The two legs of a right-angled triangle measure 12 cm and 35 cm. Its hypotenuse is:
(a) 100 cm (b) 37 cm (c) 10 cm (d) 7 cm
5. The numbers representing Pythagorean triplet are:
(a) 2, 3, 5 (b) 4, 5, 7 (c) 7, 24, 25 (d) 11, 35, 37

6. The area of a square having diagonal l is:

(a) l 2 (b) l 2 l
2
2
(c) 2 l (d) none of these

7. The number of different triangles that can be formed using 3 strips
of definite length is:
(a) 0 (b) 1
(c) 2 (d) 3

solve Mentally
True or False

1. A right-angled triangle can never be obtuse.

2. A triangle can have two obtuse angles.
3. A triangle whose two sides measure 4 cm and 400 cm is not possible.

4. The difference of two sides of a triangle is less than the third side.
5. If one side of a triangle is 8 cm, then the sum of the other two sides must be greater than
8 cm.

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