Thanks for the link. However, I couldn't do anything about the coyotes even I wanted to. I live in the city, my horse is on someone else's property in the country.
That said, it's rare for a coyote to attack a horse. Coyotes are opportunistic hunters that like to look for weak/injured/old prey, a healthy, adult horse would be difficult to catch and bring down. Sure a pack of coyotes could do it, but it would be dangerous for them, a coyote could be killed instantly will a well-placed kick, or be seriously wounded. Much like lions try to avoid attacking wildebeest because of the injury potential, I don't think a horse would be a coyote's first choice. Also if the horse was kept with other horses, as mine is, the chance of attack is even less. A herd of horses are well-equipped to defend themselves. Like zebras, they will gather in small groups of horses with similar colors/patterning to confuse predators, and they will keep mares with their foals in the center of the herd to protect them.
For anyone dealing with coyotes around horses or cattle, I will tell you what the best defense against them is: a donkey. Not kidding. While a horse's instinct tells it to run when threatened, a donkey will stay and fight. I remember at a farm nearby the owner told me his mini donkey, Eyore, pinned an aggressive stray dog to the ground and was biting and striking at it, the dog's yelps woke them up to witness this.
Here is an interesting video about guard animals (donkeys and llamas) protecting a flock of sheep from coyotes:
https://www.youtube.com/watch?v=G8oO-GypOLA
And a video about a donkey that protects calves:
https://www.youtube.com/watch?v=9z5bAfbTHWg