We need to find the size of the reflex angle $BCD$ in the given figure. We have a triangle $ABD$ with angles $33^\circ$ at $D$, $51^\circ$ at $A$, and $25^\circ$ at $B$. We need to find the reflex angle at vertex $C$.
2025/6/3
1. Problem Description
We need to find the size of the reflex angle in the given figure. We have a triangle with angles at , at , and at . We need to find the reflex angle at vertex .
2. Solution Steps
First, we calculate the angle . The sum of the angles in the triangle is .
Then, we look for the angle . We are given angle and angle . We know that is exterior angle of triangle , so
We are looking for angle . Let's look at the diagram differently.
Let angle and angle . The sum of the angles in triangle is 180, so
, giving .
The sum of the angles in triangle is 180, so
, giving .
Angle equals . Therefore, the normal angle at . But the angle should be - x. However, instead we can write , where is the interior angle at vertex .
The total angles around point is . The normal angle at is - reflex angle at C.
To determine the angle and , we can find the missing angles.
We know .
The angle = .
.
The angle at is . So
Therefore, is where X is the adjacent angle. The reflex angle should be =
Let's name the intersection . In triangle , . Therefore as they are vertically opposite angles.
Then, in triangle , the angle at C, .
Therefore the reflex angle at C, is .
3. Final Answer
317