Answer:
t = 6
∠BAC = ∠EAD = 6°
∠BCA = ∠ABC = ∠AED = ∠EDA = 87°
Step-by-step explanation:
From inspection of the diagram, we can see that there are 2 triangles inside a circle. One of the vertices of both triangles is at the center of the circle. The other vertices of both triangles are on the circumference of the circle.
The dashes on the line segments (chord) mean they are equal in length.
⇒ BC = DE
The legs of both triangles are the radius of the circle.
Therefore, ΔABC = ΔAED
This means the ∠BAC = ∠EAD, therefore:
⇒ 6t - 12 = 18 - 4t
⇒ 10t - 12 = 18
⇒ 10t = 30
⇒ t = 3
Substituting the found value of t into one of the expressions to find ∠BAC and ∠EAD:
⇒ ∠BAC = ∠EAD = 6(3) - 12 = 6°
Triangles ΔABC and ΔAED are both isosceles triangles (as they have 2 sides of equal length: the radii).
Therefore, the remaining 2 angles in each triangle will be equal.
The sum of interior angles of a triangle = 180°
⇒∠BAC + 2(∠BCA) = 180°
⇒ 6° + 2(∠BCA) = 180°
⇒ 2(∠BCA) = 174°
⇒ ∠BCA = 87°
Therefore, as ∠BCA = ∠ABC = ∠AED = ∠EDA
all the other angles are 87°
