Added surface area calculation for pyramid

Author: Cmelvank

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

@@ -21,6 +21,25 @@ private Area() {
      * String of IllegalArgumentException for base
      */
     private static final String POSITIVE_BASE = "Must be a positive base";
+	
+	/**
+	* 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;
+	}
 
     /**
      * Calculate the surface area of a cube.