<h3>
Answer: 30</h3>
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Explanation:
Let x be the unknown angle
Its supplement is 180-x, since it must add to x to get 180
The angle x is half of the supplement 180-x, meaning,
x = half of supplement of x
x = half of (180-x)
x = (1/2)*(180-x)
x = 0.5*(180-x)
x = 90 - 0.5x
x+0.5x = 90
1.5x = 90
x = 90/1.5
x = 60
The unknown angle is 60 degrees. It's supplement is 120 because 60+120 = 180, and we can see that 60 is half of 120. So that confirms we have the correct x value.
The last step is to find the complement of angle x. We subtract from 90 like so
90-x = 90 - 60 = 30 which is the final answer
As a check, we can see that 60+30 = 90 to show that we have complementary angles.
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Extra info:
It might be easy to mix up the terms "supplementary" and "complementary". What helps me remember is that "supplementary" and "straight angle" both start with S. This could be one way to remember that supplementary angles always add to 180.
Also, both "complementary" and "corner" both start with C, which may be one way to remember that complementary angles always add to 90.
