The correct answer is: [A]: "69°" . ______________________________________________________ m∠1 = 69° . ______________________________________________________ Explanation: _____________________________________________________
180 - (39 + 30) = 180 - 69 = 111. This is the measurement of the third angle in the triangle. Note that all angles in a triangle add up to 180° . All triangles have 3 (three) sides and 3 (three) angles.
To find m∠1 : _____________________________________________________ The only single angle that exists that is supplementary to ∠1 is 69.
So: m∠1 = 180 - 111 = 69 . (Note: since all angles on a straight line are supplementary angles; and supplementary angles add up to 180° . _______________________________________________________ The answer is:69° .
