This pdf covers, classifying angles on the basis of degree measurements for the proper understanding. Sample questions along with answers have also been provided.
1. Class Notes Class - V Topic - Chapter – 2 Subject - Mathematics Shapes And Angles Classification of Angles On the basis of degree measurements the angles are classified. Acute angle – An angle whose measure is more than 00 and less than 900 is called an acute angle. Example - ∠CBA is an acute angle. ∠CBA = 600 Right angle – An angle whose measure is 900 is called a right angle. Example – ∠AOB is a right angle. ∠AOB = 900 Obtuse angle – An angle whose measure is more than 900 and less than 1800 is called an obtuse angle. Example - ∠DOQ is an obtuse angle. ∠DOQ = 1200
2. Straight Angle – An angle whose measure is equal to 1800 is called a straight angle. Example - ∠XOY is a straight angle. ∠XOY = 1800 Reflex Angle – An angle whose measure is more than 1800 and less than 3600 is called a reflex angle. Example - ∠RST is a reflex angle. ∠RST = 2200 Complete Angle – An angle whose measure is equal to 3600 is called a complete angle. Example - One complete rotation around P R S a point P makes 3600 angle. Here ∠SPR = 3600 Combination of Angles Complementary Angles – Two angles are complementary if their sum is equal to 900. Example - ∠ABC = 600 , ∠CBD = 300 A Here ∠ABC + ∠CBD = 600 + 300 = 900 C So ∠ABC and ∠CBD are Complementary Angles. B D
3. Supplementary Angles – Two angles are supplementary if their sum is equal to 1800. Example - ∠BOA = 1200, ∠AOC = 600 Here ∠BOA + ∠AOC = 1200 + 600 = 1800 So ∠BOA and ∠AOC are Supplementary Angles in Clock There are 12 equal divisions in a clock for each hour. We know that one complete rotation makes 3600 angle. So angle formed between any two consecutive numbers in a clock is 360 = 12 = 300 • We can estimate the measure of angle formed by counting the number of divisions between the hour hand and minute hand multiply with 300. • We take the shortest path to do it. • We can also tell the type of angles formed. Example - At 8 ‘o’ clock the there are 4 gaps of 300 So the angle formed = 4 x 300 = 1200
4. Questions For Practice Q1. Write any 3 examples of 2D and 3D shapes. Ans . 2 Dimensional Shapes – Square, Rectangle, Triangle 3 Dimensional Shapes – Cone, Sphere, Cube Q2. Write the types of angles for the given measurement. (a) 790 (b) 1900 (c) 2890 (d) 1430 (e) 3600 (f) 1800 Ans . (a) 790 - Acute angle (b) 1900 - Reflex Angle (c) 2890 - Reflex Angle (d) 1430 - Obtuse Angle (e) 3600 - Complete Angle (f) 1800 - Straight Angle Q3. In the given figure write the names of (a) all the angles formed. (b) all the arms of the angles formed. (c) vertex of the angles. Ans. (a) All angles:- ∠DOC, ∠DOB, ∠DOA, ∠COB, ∠COA, ∠BOA (b) All arms :- DO, CO, BO, OA (C) Vertex :- O Q4. Look at the pictures given below and write the types of the angle. (a) (b) (c) Ans. (a) Acute Angle (b) Obtuse Angle (c) Right Angle
5. Q5. Look at the angles formed in the pictures given below and fill the table with tickmark for the angles. Q6. Look at the times in the clocks. Write the time and type of angles formed.
6. Q7. Fill in the blanks. (a) At _____and _____ times in the clock right angle forms. Ans. 9 ‘o’ clock, 3 ‘o’ clock (b) At ________time straight angle forms in the clock. Ans. 6 ‘o’ clock (c) Two right angles make a _____angle. Ans. Straight (d) Quarter of a complete angle is _____angle. Ans. Right 1 (e) 6 of a straight angle = ______degree. Ans. 30 Q8. Count the the number of right angles and number of angles more than right angles in the these names. (a) REENA (b) MEERA Name Number of Number of angles more right angles. than right angles. (a) REENA 8 2 (b) MEERA 8 3 The above content has been prepared absolutely from home.
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