Why does first cosine theorem work for a triangle that doesn't exist?
Given , where , , , and , what's the length of a?
The triangle doesn't exist, because the hypotenuse cannot be the same length as one of the other sides. But when you put it in the first cosine theorem, it gives an answer
The triangle doesn't exist, because the hypotenuse cannot be the same length as one of the other sides. But when you put it in the first cosine theorem, it gives an answer
???
You should know that, for a right angled triangle, the law of cosines reduces to