Explanation
We know, two angles are complementary when they add up to 90o.
Given, measure of one complementary angle is =20∘.
⇒ Measure of other complementary angle =90o−20o =70o.
∴ Measure of a complementary angle of 20∘ =70∘.
Therefore, option B is correct.
If a ray stands on a line, then the sum of two adjacent angles so formed is equal to 180∘ which is also known as a linear pair.
Consider the given triangle, we can easily apply exterior angle property of triangle.
For given triangle XYZ,
∠1+∠2+∠z=180o
Also, ∠3+∠z=180o ......... (Linear pair of angles)
∠1+∠2+∠z=∠3+∠z
⇒∠3=∠1+∠2 ...... (which is the Exterior angle property).
Therefore, we can say that, an exterior angle of a triangle is equal to the sum of the two interior opposite angles.
Hence, option A is correct.
We know, two angles whose sum is equal to 90o are known as complementary angles.
Here,
the sum, ∠2+∠3, is vetrically opposite to a perpendicular.
Given, measure of one complementary angle is 12.7o.
⇒ Measure of other complementary angle =90o−12.7o =77.3o.
∴ Measure of a complementary angle of 12.7o=77.3o.
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