The missing angle of the given triangle is 59°.
What is vertically opposite angles?
Angles that are vertically opposed to one another are always equal to one another. A vertical angle and the angle to which it is next are also supplementary angles; that is, they sum up to 180 degrees. As an illustration, if two lines connect to form an angle, say X=45°, then the angle's opposite angle is also 45°.
Here consider angle with 31° and 49° triangle is 1. We know that sum of all angles in triangle is add upto 180°. Then,
⇒ 49°+31°+x = 180°
⇒ 80° + x= 180°
⇒x= 180°-80°=100°
Then unknown angle in triangle 1 ia 100°.
Now according to the vertically opposite angle theorem , opposite angles are equal to each other. Then ,
In triangle 2 angle is 100° and 21°. Then missing angle is,
⇒ 100°+21°+missing angle =180°
⇒Missing angle = 180°-100°-21°
⇒Missing angle = 59°
Therefore the answer is 59°.
To learn more about Vertical angle ,
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