# What is the polar form of ( 7,21 )?

Mar 28, 2016

$\left(7 \sqrt{10} , {71.6}^{\circ}\right)$

#### Explanation:

To convert Cartesian to Polar coordinates , use the formula that links them.

• r = sqrt(x^2 + y^2 )

• theta = tan^-1(y/x)

here x = 7 and y = 21

$\Rightarrow r = \sqrt{{7}^{2} + {21}^{2}} = \sqrt{490} = \sqrt{49 \times 10} = 7 \sqrt{10}$

and  theta = tan^-1(21/7) = tan^-1 3 ≈ 71.6^@
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