Trig
10.9^2 = 5.8^2 + 10.5^2 - 2(5.8)(10.5) cos θ
( 10.9^2 - 5.8^2 - 10.5^2) / [ -2(5.8)(10.5) ] = cos θ
Cupcake......I get that cos θ ≈ .21
https://www.wolframalpha.com/input/?i=(+10.9%5E2+-+5.8%5E2+-+10.5%5E2)%C2%A0+%2F+%5B+-2(5.8)(10.5)+%5D
