*see attachment for diagram
Answer:
✔️m<BAC = 72°
✔️m<BCD = 108°
Step-by-step explanation:
Given:
m<ABC = (4x - 16)°
m<ACB = (5x + 7)°
Find the numerical value of m<ABC, m<ACB, m<BAC, and m<BCD.
First we need to determine the value of x.
The ∆ given is an isosceles triangle with two equal sides, therefore, the angles opposite the two equal sides would also be equal.
Therefore:
(4x - 16)° + 2(5x + 7)° = 180° (sum of ∆)
Solve for x
4x - 16 + 10x + 14 = 180
Add like terms
14x - 2 = 180
Add 2 to both sides
14x = 182
Divide both sides by 14
x = 13
Find the measure of each angle by plugging in the value of x where necessary:
✔️m<ABC = (4x - 16)° = 4(13) - 16
m<ABC = 36°
✔️m<ACB = (5x + 7)° = 5(13) + 7
m<ACB = 72°
✔️m<BAC = m<ACB (both are base angles of the isosceles ∆, so they are equal)
Therefore,
m<BAC = 72°
✔️m<BCD = m<ABC + m<ACB (exterior angle theorem of a triangle)
m<BCD = 36 + 72 (Substitution)
m<BCD = 108°
Therefore, the angle measures that are correct are:
✔️m<BAC = 72°
✔️m<BCD = 108°
