Added surface area calculation for pyramid

Author: ritgaug

src/main/java/com/thealgorithms/maths/Area.java

@@ -7,6 +7,25 @@ public final class Area {
     private Area() {
     }
 
+    /**
+* Calculate the surface area of a pyramid with a square base.
+*
+* @param sideLength side length of the square base
+* @param slantHeight slant height of the pyramid
+* @return surface area of the given pyramid
+*/
+public static double surfaceAreaPyramid(final double sideLength, final double slantHeight) {
+if (sideLength <= 0) {
+throw new IllegalArgumentException("Must be a positive sideLength");
+}
+if (slantHeight <= 0) {
+throw new IllegalArgumentException("Must be a positive slantHeight");
+}
+double baseArea = sideLength * sideLength;
+double lateralSurfaceArea = 2 * sideLength * slantHeight;
+return baseArea + lateralSurfaceArea;
+}
+
     /**
      * String of IllegalArgumentException for radius
      */