30 degree |
answer with illustration? It must be interesting to see 正三角形的威力. |
We can construct an equilateral triangle ADC with D lies on the left of the segment AC. Connects B andD. Since AD = AB, www.ddhw.com |
欢迎光临 珍珠湾ART (http://zzwav.com/) | Powered by Discuz! X3 |