Update r.fuzzy.set.html

Adapted the description of the equations to match the equations as implemented in the code. Code for linear, s-shaped and j-shaped rescaling seems OK. Not sure about the g-shape, but assuming for now that the way the equation is implemented in the code is correct.

src/raster/r.fuzzy.set/r.fuzzy.set.html

@@ -75,7 +75,7 @@ <h4>Calculation of boundary shape</h4>
 Depending on type of the boundary different equation are used to determine its
 shape:
 <p>
-<b>Linear:</b> the membership is calculated according following equation:<br>
+<b>Linear:</b> the membership is calculated according following equation:
 <pre><code>
 value  <=  A -> x = 0
 A < value > B -> x = (value-A)/(B-A)
@@ -87,33 +87,38 @@ <h4>Calculation of boundary shape</h4>
 </code></pre>
 
 <p>
-<b>S-shaped:</b> it use following equation:
+<b>S-shaped:</b> the membership is calculated according following equation:
 <pre><code>
 sin(x * Pi/2)^m (for positive shape parameter)
 1-cos(x * Pi/2)^m (for negative shape parameter)
 
 where x: membership, and
-m = 2^exp(2,shape) (for positive shape parameter)
-m = 2^(1+shape) (for negative shape parameter)
-where m: shape parameter.
+m = 2^exp(2 * |shape|) 
+For default shape=0, m = 2 (most common parameter for that equation).
 </code></pre>
 
-For default shape parameter = 0 m is = 2 which is most common parameter for
-that equation.
+<p>
+<b>G-shaped:</b> the membership is calculated according following equation:
+<pre><code>
+tan(x * Pi/4)^1/m
+
+where x: membership, and
+m = 2^exp(-2 * shape) (for negative shape parameter)
+m = 2^(1-shape) (for positive shape parameter)
+For default shape=0, m = 2 (most common parameter for that equation).
+</code></pre>
 
 <p>
-<b>G-shaped and J shaped:</b> it use following equations:
+<b>J shaped:</b> it use following equations:
 <pre><code>
-tan(x * Pi/4)^m (for J-shaped)
-tan(x * Pi/4)^1/m (for G-shaped)
+tan(x * Pi/4)^m
 
 where x: membership, and
-m = 2^exp(2,shape) (for positive shape parameter)
+m = 2^exp(2 * shape) (for positive shape parameter)
 m = 2^(1+shape) (for negative shape parameter)
-where m: shape parameter.
+For default shape=0, m = 2 (most common parameter for that equation).
 </code></pre>
 
-
 <h2>SEE ALSO</h2>
 
 <em>