What happen if the angle in the circle segment is right angle? What kind of segment do you obtain? Draw the figure and give reason.

Draw four congruent circles as shown. What do you infer ?

Prove that the angle between the two tangents drawn from an external point to a circle is supplementary to the angle subtended by the line - segment joining the points of contact at the centre.

What is angle of polarisation and obtain the equation for angle of polarisaition.

What is the resultant vectors , when two vectors are at right angles to each other ?

Protoxylem is the first formed Xylem. If the protoxylem is surrounded by phloem what kind of arrangement of xylem would you call it ? Give an example.

Procedure : (i) Draw three circles of any radius with centre O on chart paper. (ii) From these circles, cut a semi - circle, a minor segment and a major segment (iii) Consider three points on these segment and name them as A,B, and C (iv) Cut the triangles and paste it the graph sheet so that the point A coincides with the origin as shown in the figure. Ovservation : (i) Angle in a Semi - Circle is . . . . . . . . . . angle. (ii) Angle in a major segment is angle. (iii) Angle in minor segment is . . . . . . . angle.

Find the measure of angle ‘a’ in each figure. Give reason in each case .

Angle sum for a polygon Draw any quadrilateral ABCD. Mark a point P in its interior. Join the segments PA, PB, PC and PD You have 4 triangles now. How much is the sum of all the angles of the 4 triangles ? How much is the sum of the angles at P ? Can you now find the 'angle sum' of the quadrilateral ABCD ? Can you extend this idea to any polygon ?