use approximate calculation for power function

Author: shaoziyang

LPS22.ts

@@ -143,11 +143,17 @@ namespace LPS22 {
         return Math.round(P)
     }
 
+    // power function approximate calculation for (1+x)^n, x~0
+    export function apow(x: number, n: number): number {
+        let d = x - 1
+        return 1 + (n * d) + (n * (n - 1) * d * d) / 2
+    }
+
     /**
      * calaulate altitude use pressure and temperature
      */
     //% block="altitude"
     export function altitude(): number {
-        return (((1013.25 / pressure()) ** (1 / 5.257)) - 1.0) * (temperature() + 273.15) / 0.0065
+        return (apow(1013.25 / pressure(), 1 / 5.257) - 1.0) * (temperature() + 273.15) / 0.0065
     }
 }