The word quad means four and the word lateral means sides. Thus, a plane figure bounded by four line segments AB, BC, CD and DA is called a quadrilateral and is written as quad. ABCD or, ABCD. The points A, B, C, D are called its vertices. The four line segments, AB, BC, CD and DA are the four sides, and the four angles , , and are the four angles of quad. ABCD, Two line segments AC and BD are called the diagonals of quad. ABCD.
GIVEN Quadrilateral ABCD To Prove <A + <B + <C + <D = 360 Construction Join BD Proof: In ABD, we have <1 + <2 + <3 = 180 .....(i) In BCD, we have <4 + <5 + <6 = 180 .......(ii) Adding (i) and (ii), we get <1 + <2 + <3 + <4 + <5 + <6 = 180 + 180 <1 + (<2 + <6 )+ <5+ (<3 + <4) = 180 + 180 <A + <B + <C + <D = 360 <A + <B + <C + <D = 360 |
Illustration: In a quadrilateral ABCD, the angles A, B, C and D are in the ratio 1 : 2: 3 : 4. Find the measure of each angles of the quadrilateral.
Solution: We have, <A : <B : <C : <D = 1 : 2 : 3 : 4. So, let <A = x, <B = 2x, <C = 3x, < D = 4x.
<A + <B + <C + <D = 360
x + 2x + 3x + 4x = 360 10x = 360 x = 36
Thus, the angles are
Which of the following is a formula to find the sum of interior angles of a quadrilaters of n-sides? | |||
Right Option : D | |||
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Find the value of x when other three angles of four sided figure are 30, 75, 150. | |||
Right Option : C | |||
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The angle of a quadrilateral are (3 x + 2)°, (x – 3), (2 x + 1)°, 2(2 x + 5)° respectively. Find the measure of each angle. | |||
Right Option : A | |||
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