The '''SQR''' function returns the square root of a numerical value.


{{PageSyntax}}
:: square_root = '''SQR('''value''')'''


* The ''square root'' returned is normally a [[SINGLE]] or [[DOUBLE]] numerical value.
* The ''value'' parameter can be any '''positive''' numerical type. '''Negative parameter values will not work!'''
* Other exponential root functions can use fractional exponents([[^]]) enclosed in '''parenthesis only'''. EX: {{text|root <nowiki> = </nowiki> c ^ (a / b)|green}}


''Example 1:'' Finding the hypotenuse of a right triangle:
{{CodeStart}} '' ''
 A% = 3: B% = 4
 PRINT "hypotenuse! ="; SQR((A% ^ 2) + (B% ^ 2)) '' ''
{{CodeEnd}}
{{OutputStart}}
 hypotenuse = 5
{{OutputEnd}}


''Example 2:'' Finding the Cube root of a number. 
{{CodeStart}} '' ''
 number = 8
 cuberoot = number {{Cl|^}} (1/3)
 PRINT cuberoot '' ''
{{CodeEnd}}
{{OutputStart}}
 2
{{OutputEnd}}


''Example 3:'' Negative roots return fractional values of one.
{{CodeStart}} '' ''
 number = 8
 negroot = number {{Cl|^}} -2
 PRINT negroot '' ''
{{CodeEnd}}
{{OutputStart}}
 .015625
{{OutputEnd}}
:''Explanation:'' A negative root means that the exponent value is actually inverted to a fraction of 1. So x ^ -2 actually means the result will be: 1 / (x ^ 2).


''Example 4:'' Fast Prime number checker limits the numbers checked to the square root (half way).
{{CodeStart}}
DEFLNG P
DO
PRIME = -1   'set PRIME as True
INPUT "Enter any number to check up to 2 million (Enter quits): ", guess$
PR = {{Cl|VAL}}(guess$)
IF PR {{Cl|MOD}} 2 THEN              'check for even number
  FOR P = 3 TO {{Cl|SQR}}(PR) STEP 2 'largest number that could be a multiple is the SQR
    IF PR {{Cl|MOD}} P = 0 THEN PRIME = 0: EXIT FOR 'MOD = 0 when evenly divisible by another
  NEXT
ELSE : PRIME = 0 'number to be checked is even so it cannot be a prime
END IF
IF PR = 2 THEN PRIME = -1 '2 is the ONLY even prime
IF PR = 1 THEN PRIME = 0  'MOD returns true but 1 is not a prime by definition
IF PRIME THEN PRINT "PRIME! How'd you find me? " ELSE PRINT "Not a prime, you lose!"
LOOP UNTIL PR = 0 '' ''
{{CodeEnd}}
{{OutputStart}}
Enter any number to check up to 2 million (Enter quits): 12379
PRIME! How'd you find me?
{{OutputEnd}}
<center>''Note:'' Prime numbers cannot be evenly divided by any other number except one.</center>


''See also:'' 
*[[MOD]] {{text|(integer remainder division)}}
*[[^]] {{text|(exponential operator)}}
*[[Mathematical Operations]]
*[[Mathematical_Operations#Derived_Mathematical_Functions|Derived Trigonometric Functions]]


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