This question was uploaded on 25/12/21 on social media accounts.
Solution 1:
By using Ptolemy's Theorem,
\[ax + bx = cy\]
\[\Rightarrow a + b = c\left(\frac xy\right)\]
Given that:
\[a + b = c\]
By comparing both equations:
\[\frac xy = 1\Rightarrow x=y\]
By this, the triangle with sides x, x, y is an equilateral triangle,
\[\Rightarrow 180-2\theta = 60\]
\[\Rightarrow \theta = 60\]
Solution 2:
Clearly a + b = c and θ = 60°
