mathsteps-experimental-fork/dist/cjs/lib/simplifyExpression/rules/sqrtFromPow.js

Step by step math solutions. Experimental Fork

'use strict';

const config = require('../../config.js');
const clone = require('../../newServices/nodeServices/clone.js');
const index = require('../../node/index.js');
const ChangeTypes = require('../../types/changeType/ChangeTypes.js');

function sqrtFromPow(node, simplifyCtx) {
  let rv = null;
  // eslint-disable-next-line eqeqeq
  if (index.default.Type.isFunction(node, 'sqrt') && node.args[0].op == '^') {
    const root = node.args[0].args[0];
    const exponent = node.args[0].args[1];
    if (index.default.Type.isConstant(exponent)) {
      const exponentValue = exponent.value;
      const exponentMod2 = config.default.mod(exponentValue, 2);
      const exponentMod4 = config.default.mod(exponentValue, 4);
      if (config.default.equal(exponentMod2, 0)) {
        // sqrt(x^2)     gives |x|   or x
        // sqrt(x^(2*n)) gives |x|^n or x^n
        let newNode = null;
        let rootIsNonNegative = false;
        if (simplifyCtx.expressionCtx)
          rootIsNonNegative = simplifyCtx.expressionCtx.isNodeNonNegative(root);

        if (config.default.equal(exponentValue, 2)) {
          // sqrt(x^2)
          if (rootIsNonNegative) {
            // sqrt(x^2) gives x if x>=0
            newNode = clone(root);
          }
          else {
            // sqrt(x^2) gives |x| if x can be negative
            newNode = index.default.Creator.kemuCreateAbs(root);
          }
        }
        else if (rootIsNonNegative || config.default.equal(exponentMod4, 0)) {
          // sqrt(x^2n) gives x^n if x>=0
          // sqrt(x^4n) gives x^2n for any x
          const newExponent = index.default.Creator.operator('/', [clone(exponent), index.default.Creator.constant(2)]);
          newNode = index.default.Creator.operator('^', [clone(root), newExponent]);
        }
        if (newNode) {
          rv = {
            changeType: ChangeTypes.ChangeTypes.KEMU_SQRT_FROM_POW,
            rootNode: newNode,
          };
        }
      }
    }
  }
  return rv
}

module.exports = sqrtFromPow;