Page 2 - ln1

(i) Interior angles are 50 and 70
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Exterior angle= [Sum of interior opposite angles]

x=50 +70 =120
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Angle sum property of a triangle:

The total measure of the three angles of a triangle is 180 .
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In △PQR,

∠RPQ+∠PQR+∠QRP =70 + 60 + 50 =180
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Example:

1. Find the value of the unknown x in the following diagrams

Sum of interior angles of a triangle =180
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x+2x+90 =180
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3x + 90 =180
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3x = 180 − 90
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x=90 /3=30
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2. Find the values of the unknowns x and y in the following diagrams.