(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[백 Cho Hye Yeon 9p]PB[흑 my friends 2dan]C[Today's topic is the diagonal tesuji (including the symmetrical diagonal).
]
(;B[pd]
;W[nc]
;B[ob]
;W[qf]
;B[oe]
;W[qc]
;B[re]C[White to play 
]
;W[rb]C[This is the symmetrical tesuji.
]
;B[oc]
;W[qe]C[White succeeds!
])
(;B[dp]
;W[fq]
(;B[dd]
;W[cn]
;B[eo]
;W[cq]C[This is a joseki. After this black usually plays tenuki again and treats his 2 stones in this corner lightly. ]
;B[pd]
(;W[cp]C[It is normal for white to choose to connect to one of the two sides later. ])
(;W[dq])
(;W[br]C[But if white really wants to connect all his stones, this is the move! This does leave some big aji.]))
(;B[fp]
;W[gp]
;B[fo]
;W[eq]
;B[dq]
;W[go]
;B[dn]
;W[io]
;B[iq]
;W[pp]
;B[gn]
;W[qo]C[Black to play!
]
;B[hp]C[This is the diagonal tesuji! 
]
;W[ho]
;B[gq]C[Black succeeds!
]
;W[pc]
;B[pe]
;W[ph]
;B[md]
;W[oe]
;B[of]
;W[ne]
;B[pd]
;W[nc]
;B[qc]
;W[oc]
;B[nf]
;W[me]
;B[rd]
;W[ic]
;W[mf]C[After joseki white sometimes wants to play here. Be careful as black!]
(;B[nh]C[This looks natural but this is wrong.]
(;W[pf]
;B[pg]
;W[og]
;B[qf]
;W[ng])
(;W[og]
;B[ng]
;W[pf]))
(;B[oh]C[The correct shape.])))
(;AW[fj][ck][ek][in][do][dp][ep][ip][bq][cq][hq][br][cr]AB[qk][qm][cn][co][eo][qo][cp][pp][dq][eq][fq][oq][dr]C[Black to play!]
(;B[fp]
;W[dn]
;B[dm]
;W[en]
;B[fm]
;W[fo]
(;B[go]
;W[em]C[Black is in danger!
])
(;B[fn]
;W[go]C[Black is not good.
]))
(;B[dn]
;W[fp]
;B[gp]
;W[fo]
;B[gn]
;W[en]
;B[em]
;W[go]C[Black fails to capture white.
])
(;B[fn]C[This is a symmetrical tesuji.
]
(;W[dn]
;B[dm]
;W[fp]
;B[gp]C[White is dead.
])
(;W[fo]C[White plays here, and then...
]
;B[go]
;W[en]
;B[em]
(;W[fm]
(;B[fp]C[This is a black's mistake.
]
;W[dn]
;B[dm]
;W[gn]C[Black is destroyed.
])
(;B[gn]C[Black should connect here.
]
;W[dm]
;B[dn]
;W[el]
;B[fp]C[White is dead.
]))
(;W[gn]
;B[fm]
;W[gp]
;B[fp]
;W[ho]
;B[dn]C[White cannot be alive.
]))
(;W[fp]
;B[gp]
;W[en]
;B[dn]C[White cannot get out.
])
(;W[en]
;B[em]
;W[fo]
;B[go]C[White cannot escape due to the effect of the diagonal.
])))
(;B[qd]
;W[dd]
;B[oc]
;W[dp]
;B[pq]
;W[po]
;B[qm]
;W[qq]
;B[qr]
;W[qp]
;B[mq]
;W[om]
;B[pm]
;W[ol]
;B[pk]
;W[or]
;B[pr]
;W[oq]
;B[pp]
;W[op]
;B[qo]
;W[ro]
;B[oo]
;W[pn]
;B[qn]
;W[on]
;B[rr]
;W[no]C[This is an "old" joseki. Black needs to be careful and come back now. ]
(;B[pj]C[This is the right move. If black plays tenuki, white can cut!])
(;B[iq]C[Wrong. ]
;W[pl]
;B[ql]
;W[qk]
;B[qj]
;W[rk]
;B[rj]
;W[rl]
;B[rp]
;W[rn]
;B[rq]
;W[qp]
;B[qq]
;W[rm]
;B[qp]
;W[pj]
;B[ok]
;W[pi]C[This move makes miai. ]
;B[ss]C[Also black still needs to live in the corner! This is the tesuji to live. But ofcourse this is a terrible result for black. ]))
(;AW[pd][fj][dm][pp]AB[dd][dj][dp][fp]
;B[el]
;W[em]C[Black to play
]
;B[fk]C[This is recommended!
]
;W[gk]
;B[fl]C[The second tesuji - empty triangle.
])
(;AW[cl][bm][an][bo][ap][bp][bq][hq][cr][dr][er][gr][ds][fs]AB[bn][cn][co][ho][cp][gp][cq][dq][eq][fq][br][fr]C[Black to play. ]
;B[as]C[Symmetrical diagonal tesuji!
]
;W[es]
;B[aq]))
