Putuq, Pilla t'asra icha Inkapunku (kastilla simimanta: trapecio) nisqaqa iskay chimpa kaq chimpanasqa (chasllasqa) kaq chiruyuq kaq, wakin chiruntaq mana chimpanasqa kaptintaqmi.
f = a 2 + d 2 − 2 a d cos α = b 2 + c 2 − 2 b c cos γ {\displaystyle f\,=\,{\sqrt {a^{2}+d^{2}-2\,a\,d\,\cos \alpha }}={\sqrt {b^{2}+c^{2}-2\,b\,c\,\cos \gamma }}}