The distance between the points A(a cos 20∘ + b sin20∘, 0) and B(0, a sin20∘ - b cos20∘) is:
√a2+b2
AB2 = (acos20∘+bsin20∘)2 + (asin20∘−bcos20∘)2
AB2 = (a2cos220∘+b2sin220∘+2abcos20∘sin20∘+a2sin220∘+b2cos220∘−2abcos20∘sin20∘)
AB2 = a2(cos220∘+sin220∘)+b2(cos220∘+sin220∘)
AB2 = a2 + b2
AB = √a2+b2