Question

23 find the measure of the unknown angle in each triangle and mark the column with the correct answer. triangle 50° 58° 30 40° 65°? 57° 40°? 20° 130°?

Explanation:

Step1: Recall angle - sum property

The sum of interior angles of a triangle is 180°.

Step2: Calculate first unknown angle

For the first triangle with angles 65° and 57°, let the unknown angle be $x$. Then $x = 180-(65 + 57)=180 - 122 = 58^{\circ}$.

Step3: Calculate second unknown angle

For the second right - triangle with one angle 40° and a right - angle (90°), let the unknown angle be $y$. Then $y=180-(90 + 40)=180 - 130 = 50^{\circ}$.

Step4: Calculate third unknown angle

For the third triangle with angles 20° and 130°, let the unknown angle be $z$. Then $z = 180-(20+130)=180 - 150 = 30^{\circ}$.

Answer:

For the first triangle, mark the column with 58°.
For the second triangle, mark the column with 50°.
For the third triangle, mark the column with 30°.