One of the equal angles of an isosceles triangle is 40°. Find its other angle.

Name each polygon. Make two more examples of each of these.

Construct two line segments AB and CO of lengths 2.5 cm and 3.2 cm. Construct another segment EF, whose length is the sum of these two segments. Measure the new length.

Name the type of triangle, if
(a) sides are 7 cm, 8 cm and 9 cm
(b) ΔABC; AB = AC = 6 cm, BC = 8 cm
(e) ΔABC; AB = BC = AC = 5 cm
(d) ΔABC; \(\angle B = 90°\), BC= 4 cm, AB = 3 cm.

In figure, BCDE is a square and a 3-D shape has been formed by joining the point A in space with the vertices B, C, D and E. Name the 3-D shape and also its
(i) vertices
(ii) edges and
(iii) faces.

During Maths lab activity, each student was given four broomsticks of length 8 cm, 8 cm, 5 cm, 5 cm to make different types of quadrilaterals.
(a) How many quadrilaterals can be formed using four broomsticks?
(b) Name the types of quadrilateral formed.
(c) While doing this activity, which value is depicted?

If line segment AB = 10 cm and C, D, E, F are four points at line segment AB, such that AC = CD = DE = EF = FB. Then, find measure of AD.

Place a pair of unequal sticks such that they have their end points joined at one end. Now place another such pair meeting the free ends of the first pair.
What is the figure enclosed? It is a quadrilateral, like the one you see here.
The sides of the quadrilateral are \(\overline { AB } \), \(\overline { BC } \) ,...,

There are 4 angles for this quadrilateral. They are given by \(\angle\)BAD, \(\angle\)ADC, \(\angle\)DCB and.
\(\overline { BD } \) is one diagonal. What is the other?
Measure the length of the sides and the diagonals. Measure all the angles also.

Using a protractor and a ruler find the measures of the sides and angles of the given triangles. Fill the measures in the given table.
(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

Observe the angles and the triangles as well as the measures of the sides carefully. Is there anything special about them?
What do you find?
(i)Triangles in which all the angles are equal. If all the angles in a triangle are equal, then its sides are also _____________.
(ii)Trianges in which all the sides are equal. If all the sides in a triangle are equal, then its angles are___________ .
(iii)Triangles which have two equal angles and two equal sides. If two sides of a triangle are equal, it has __________ equal angles and if two angles of a triangle are equal, it has___________ equal sides.
(iv)Triangles in which no two sides are equal. If none of the angles of a triangle are equal then none of the sides are equal. If the three sides of a triangle are unequal then, the three angles are also___________.

You have two set-squares in your instrument box. One is 30°-60°-90° set square, the other is 45°- 45°-90° set square.
You and your friend can jointly do this.
(a) Both of you will have a pair of 30°-60°- 90° set squares. Place them as shown in the figure. Can you. name the quadrilateral described? What is the measure of each of its angles? The quadrilateral is a rectangle. One more obvious property of the rectangle you can see is that opposite sides are of equal length. What other properties can you find?

(b) If you use a pair of 45°-45°-90° set squares, you get another quadrilateral this time.
It is a square.

Are you able to see that all the sides are of equal length? What can you say about the angles and the diagonals? Try to find a few more properties of the square.
(c) If you place the pair of 30°-60°-90° set squares in a different position, you get a parallelogram. Do you notice that the opposite sides are parallel? Are the opposite sides equal? Are the diagonals equal?

(d) If you use four 30°-60°-90° set squares you get a rhombus.
(e) If you use several set-squares you can build a shape like the one given here. Here is a quadrilateral in which two sides are parallel.

It is a trapezium.
Here is an outline-summary of your possible findings. Complete it.