How many degrees is angle x?
A normal-level "Angle" problem."Vertically opposite angles are equal" is not a rule to memorise — you can rebuild it from "a straight line is 180°". It turns up in geometry problems endlessly.
GivenTwo straight lines cross at a point
Hints
- Colour just the horizontal line. Above it two angles sit side by side, and a straight line is 180°.
- The neighbouring angle is what is left of 180° after 55°: 180 − 55 = 125°.
- Now colour the other line. It is straight too, so the two angles along its left side also total 180°.
- Those two are the 125° we just found and the x we want. So x = 180 − 125.
- The result is the same 55° as the original angle. Using "a straight line is 180°" twice always does this: vertically opposite angles are always equal.
Answer 55°
More "Angle" problems
- How big is angle x?
- How many degrees is angle x?
- What is A＋B＋C＋D＋E?
- How big is angle BIC?
- How many degrees is angle x?
- How many degrees is angle x?