AM-967

R-formula

A Math · Secondary 3 · Hard · R-formula

The distance of a ship from a harbour is modeled by

D = 6 + 5\sin\theta + 5\cos\theta

, where

D

is in km and

\theta

is in degrees.
Express

D

in the form

D = p + R\cos(\theta - \alpha)

, where

R>0

and

0^\circ<\alpha<90^\circ

.
What is the value of

R

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