= ⁄2 ǤС cos = 0 Ȥʤ롣
Ĥޤꡢ;üʾȤơԥ饹(Pythagorean theorem)Ȥʤ롣
ˡ裱;
a = b cos + c cos
Ƴ롣
ˡabc 줾˳ݤȰʲΤ褦ˤʤ롣
ǡ裱裲ơդ裱裲裳ŬѤȡ
Ȥʤ롣