Challenge the class to figure out sin57 with just a ruler and protractor - no calculator. Hopefully some bright spark will put the equipment together with last night's homework, and draw a right-angled triangle with a diagonal of 1.

So, same challenge - cos23. This time, draw the triangle yourself, putting the 'angle' in the same place.

Finally, draw the unit circle in. Pick a third point on the circle, in the same quadrant. Draw an 'x' there.

"What's special about this point?"

Hopefully someone (perhaps someone who's done the homework) will now tell you that you should draw the triangle, and that the two straight sides will give you sin and cos of the angle.

## Alert!

**Hello, reader! If you intend to post a link to this blog on Twitter, be aware that for utterly mysterious reasons, Twitter thinks this blog is spam, and will prevent you from linking to it. Here's a workaround: change the .com in the address to .ca. I call it the "Maple Leaf Loophole." And thanks for sharing!**## Wednesday, February 2, 2011

### We Have a Winner

Alex, on Files for Riley's Intro to Trig, asking the question backwards and displaying the kind of lesson-design genius that I wish came easily to me:

## Tuesday, February 1, 2011

### Files for Riley's Intro to Trig

I assigned this to be done outside class today, since tomorrow's lesson is "Trig on the Unit Circle." You should go read it because otherwise I'd just be copying and pasting the whole thing.

I'm a little flail-y, still, about where to take it tomorrow. I have never had success getting the cherubs to see the connection between the coordinates on the unit circle and sine and cosine. Or when I have, it's been fleeting. I was thinking we'd discuss the patterns and shortcuts, and then I'd pose "Let's come up with a way to find precise coordinates for 57.4 degrees without having to draw it." But I'd love to hear better ideas.

Anyway, I thought it would be helpful to make the files I'm using available. They are here. One's a GSP and the other is an Excel.

I'm a little flail-y, still, about where to take it tomorrow. I have never had success getting the cherubs to see the connection between the coordinates on the unit circle and sine and cosine. Or when I have, it's been fleeting. I was thinking we'd discuss the patterns and shortcuts, and then I'd pose "Let's come up with a way to find precise coordinates for 57.4 degrees without having to draw it." But I'd love to hear better ideas.

Anyway, I thought it would be helpful to make the files I'm using available. They are here. One's a GSP and the other is an Excel.

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