If by triangle, you refer to the Greek letter delta [Δ], then it means change. So if you see ΔT, this means a change in temperature, if that is the context.
The letter Δ can be applied to many variables, such as (depending on context) Δv could mean a change in velocity, or Δx could mean a change in position in the x direction, and Δy can mean a change in position in the y direction, so Δy/Δx is [change in y] divided by [change in x] which is the slope.
changed
the temperature has changed
To indicate the temperature?
It means that it's a triangle with a certain amount of temperature in degrees Fahrenheit. It could also mean that a certain triangle has a temperature inside it.
It means the temperature has changed.
reached the maximum level allowed.
The triangle notation in music represents a percussion instrument called the triangle. It is used to indicate when and how the triangle should be played in a musical piece, adding a unique sound and rhythm to the composition.
Tick marks indicate when lines or angles are congruent.
It is a "!" is a yellow triangle
You do not indicate if the given area is the total area of the square and the triangle. Or whether they are equal values.
A triangle on a map typically represents a mountain peak or summit. It is often used to indicate the highest point of elevation in that particular area.
Fahrenheit and Celsius