 Hi, I'm Zor. Welcome to your new Zor education. We are about to explain another very, very short topic, how one particular trigonometric function, in this case, at second, behaves for basic angles. Now, the basic angles are like 30-degree, 45-degree, etc. So, I will list them here, and I will derive the value of the second for these angles. And I will do it very easily because, by definition of the second, that's 1 over cosine. So, if I know the cosine for these basic angles, I can very easily find what's the second. So, basic angles, 0 reagents, 5 over 6, 5 over 4, 5 over 3, and 5 over 2, which is 0 degrees, 30 degrees, 45 degrees, 60 degrees, 90 degrees. So, what's the value of my cosine? Well, for 0 it's 1, if you remember. For 5 over 6, 30 degrees, that's the cosine. So, it's square root of 3 over 2. This is square root of 2, this is 1, half, and this is 0. So, great. What's my second in this case? Well, 1 over, 1 over 1 is 1. This is 2 over square root of 3, which is equal to... I prefer, actually, to have the square root operation in the numerator. That's how it's traditional. So, I will multiply by square root of 3 both. So, it's 2 square root of 3 over 3. Now, this is reverse. So, it's 2 over square root of 2, which is equal to... I just think if you multiply by square root of 2, you will have 2 square root of 2 over 2, so it's square root of 2. Now, this is 2, and this doesn't exist, because the cosine is equal to 0, that's the denominator. Now, cosine is an even function. That makes second even function. Even function, the value of negative angles is exactly the same as positive. And also, you know that 2 pi is a period, so you can always add 2 pi to any angle. And that's how you can derive, basically, to any nice angle around the circle. What might also help is that the cosine of x plus pi is equal to minus cosine of x, and that makes exactly the same rule. That's why it makes exactly the same rule for a second, so you can always add pi or 180 degree to an angle. So, all these nice angles can be derived, and the values can be derived from these. That's it. It's a very short lecture. Again, my purpose was to explain how the second behaves in these major angles. And the only thing which is left, I think I've covered everything except cos second, which will be the next lecture. So, thanks very much for listening to me today. And so, next is a cos second. Thank you.