user10887: Does Black's pinned knight on g4 protect the bishop on f2 from the white king?
B2N4/8/3p2p1/Q2P4/4R1nk/7b/PPP2bpP/1R4K1 w - - 0 1


user4362: This is checkmate. 
According to the fide rules (bold by me):
1.2
The objective of each player is to place the opponent’s king ‘under attack’ in such a way that the opponent has no legal move. The player who achieves this goal is said to have ‘checkmated’ the opponent’s king and to have won the game. Leaving one’s own king under attack, exposing one’s own king to attack and also ’capturing’ the opponent’s king are not allowed. The opponent whose king has been checkmated has lost the game.
3.9
The king is said to be 'in check' if it is attacked by one or more of the opponent's pieces, even if such pieces are constrained from moving to that square because they would then leave or place their own king in check. No piece can be moved that will either expose the king of the same colour to check or leave that king in check.

10887: <p>Does Black's pinned knight on <code>g4</code> protect the bishop on <code>f2</code> from the white king?</p>

<pre><code>B2N4/8/3p2p1/Q2P4/4R1nk/7b/PPP2bpP/1R4K1 w - - 0 1
</code></pre>
 4362: <p>This is checkmate. </p>

<p>According to the fide rules (bold by me):</p>

<p>1.2<br>
The objective of each player is to place the opponent’s king ‘under attack’ in such a way that the opponent has no legal move. The player who achieves this goal is said to have ‘checkmated’ the opponent’s king and to have won the game. Leaving one’s own king under attack, exposing one’s own king to attack and also ’capturing’ the opponent’s king are not allowed. The opponent whose king has been checkmated has lost the game.</p>

<p>3.9<br>
The king is said to be 'in check' if it is attacked by one or more of the opponent's pieces, <strong>even if such pieces are constrained from moving to that square because they would then leave or place their own king in check</strong>. No piece can be moved that will either expose the king of the same colour to check or leave that king in check.</p>
