Answer:
18.7
Step-by-step explanation:
The Law of Cosines is , where c is the unknown side length of a triangle, a and b are the remaining two side lengths, and C is the angle opposite to side c. To answer this question just plug in the known values:
Simplify:
m≈18.665...
When rounded to the nearest tenth, m=18.7
By angle addition postulate,
m(∠ABD) + m(∠DBC) = m(∠ABC)
Now substitute the values of each angle,
(5x + 5)° + (3x + 12)° = 153°
Combine like terms of the expression,
(5x + 3x) + (5 + 12) = 153
8x + 17 = 153
8x = 153 - 17
x =
x = 17
Substitute the value of 'x' to get the measure of each angle,
m(∠ABD) = (5x + 5)
= 5(17) + 5
= 90°
m(∠DBC) = (3x + 12)
= 3(17) + 12
= 63°
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