Find all the unknown angle measures in the diagram. Justify your answer for each angle measure.
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Answer:
∠1 is 90° because it is a right angle
To find angle 2, we must add the given angles and x then make the equation equal to 180°, which we next solve for x;
x + 90 + 30 = 180
x + 120 = 180
-120 -120
x = 60, ∠2 = 60°
Angle 5 is vertical to angle 1 which equals 90 degrees, and vertical angles are congruent meaning that they measure the same degrees so therefore ∠5 = 90°
Angles 4 and 40° are vertical to angle 2 which measures 60 degrees;
40 + x(where x equals angle 4) = 60
-40 -40
x = 20, ∠4 = 20°
Specified earlier, angles 40° and 4 are equal to 60°, this means that angle three added to angles 40° and 4 will be equal to 90 degrees since angle 1 is 90 degrees and the other three angles will have to equal 90 degrees because they are supplementary.
So we set up the equation;
40 + 20(angle four) + x = 90
60 + x = 90
-60 -60
x = 30, ∠3 = 30°