<prompt> Tuseme kwamba kuna pembetatu mbili zinazolingana pembetatu ABC na pembetatu ACD kiasi kwamba AB AC AD, kama inavyoonyeshwa kwenye mchoro ufuatao. Ikiwa angle BAC 20circ, basi angle BDC ni nini? asyjozi pA, pB, pC, pD;pA 0, 0;pB pA dir 240;pC pA dir 260;pD pA dir280;chorapA--pB--pC--pA;chorapA--pC--pD--pA;leboA, pA, N;leboB, pB, SW;leboC, pC, S;leboD, pD, E;asy  <response>: Kwanza tunachora BD: asyjozi pA, pB, pC, pD;pA 0, 0;pB pA dir 240;pC pA dir 260;pD pA dir280;chorapA--pB--pC--pA;chorapA--pC--pD--pA;chorapB--pD,nyekundu;leboA, pA, N;leboB, pB, SW;leboC, pC, S;leboD, pD, E;asy Kwanza, tunaona kwamba pembetatu ABC ni isosceles; kwa hiyo angle ACB angle ABC frac12cdot180circ-20circ 80circ. Vivyo hivyo, angle ACD angle ADC 80circ. Sasa, tunaona kwamba angle BCD pembe ACB angle ACD 160circ.Kisha, tunaona kwamba pembetatu BCD ni isosceles pia. Hiyo inamaanisha angle CBD angle BDC frac12cdot180circ-160circ 10circ, kama unavyotaka. 