# XWUIChartTangent

A tangent chart: a fixed-type wrapper around `XWUIChart` that plots a series together with its tangent or slope at points, emphasizing the rate of change along the curve. Supply `{ series }` of `{ x, y }` points plus a `block` preset (1-4) and `size`. Use it to highlight where a trend is rising or falling fastest, not just its level.

## Basic Usage

This example plots the two series, Series A and Series B, across their six monthly points (Jan through Jun) and draws the tangent at each, so the steepest month-to-month rises and falls are easy to spot at medium size.

```example
file: examples/BasicUsage.ts
html: examples/BasicUsage.html
title: Basic Usage
description: The two series plotted with their tangents across the six monthly Jan-Jun points, surfacing where each trend changes fastest.
```

## Projectile Height vs Time

A smooth parabolic trajectory traces a thrown object's height each half-second; the tangent reveals its vertical velocity - steeply positive at launch, zero at the apex, and increasingly negative on the way down.

```example
file: examples/ProjectileHeight.ts
html: examples/ProjectileHeight.html
title: Projectile Height vs Time
description: A parabolic flight path whose tangent gives the vertical velocity at every instant, vanishing at the apex.
```

## Coffee Cooling Curve

A cup of coffee relaxing toward room temperature follows an exponential-decay curve; the tangent makes the cooling rate visible - steep while the gap is large, then flattening as it nears room temperature.

```example
file: examples/CoolingCurve.ts
html: examples/CoolingCurve.html
title: Coffee Cooling Curve
description: An exponential cooling curve whose tangent shows the falling rate of heat loss as temperature approaches the room's.
```

```api
```