(python)Triangular Numbers (two parts!): (3 pts)

Part 1 (2pts) Write a function called triang(n) that uses recursion to return the sum

+(1)+(2)++1.n+(n1)+(n2)++1.

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def triang(n):

 # YOUR CODE HERE

 raise NotImplementedError()

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assert triang(3) == 6

assert triang(10) == 55

(python)Part 2 (1pt- manually graded) Add a docstring to the code of triang(n) so that when you call help(triang) it explains what the function does.

In [ ]:

# YOUR CODE HERE

raise NotImplementedError()

Use recursion to write a function printBackwards(x) that takes in a string and prints it backwards.

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def printBackwards(x):

 # YOUR CODE HERE

 raise NotImplementedError()

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assert printBackwards('taco') == 'ocat'

assert printBackwards('Was it a cat i saW') == 'Was i tac a ti saW'

Use two arguments, where the second argument is the number you're checking divisibility by. Give this one a default value as in the code below.

def isPrime(n,i=2): if i> n/2: return True # Your Solution here

(python)Complete the function isPrime below.

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def isPrime(n,i=2):

 # YOUR CODE HERE

 raise NotImplementedError()

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assert isPrime(3) == True

assert isPrime(17) == True

assert isPrime(20,6) == False

(python)Complete the following test function testPrime(n) that illustrates the result of calling isPrime(i) on i=1,...,n

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def testisPrime(n):

 # YOUR CODE HERE

 raise NotImplementedError()