Video narration
What does sin θ measure on a playground slide? Imagine the slide as a right triangle. If θ is at the bottom, the vertical rise is across from it: that's the opposite side. The slope is the hypotenuse, the triangle's longest side. Move θ, and the opposite side changes, because "opposite" depends on which angle you choose. Here's the flip: sin θ is not itself a height or a length; it compares the two. So put the rise on top and the slope underneath: sin θ equals opposite side divided by hypotenuse. For a five-metre rise and a ten-metre slide, divide five by ten. Sin θ is zero point five, meaning half the slope's length shows up as vertical height. So what does sin θ measure on that slide? The vertical rise as a fraction of the slope's length.