Question

(c) Find the equations of the curves whose parametric equations are:

ii) x = 3cos theta , y = 3sin theta

Answer 1

The aim is to eliminate the parameter theta....the final eqn should be a relationship between x and y

Answer 2

x = 3cos t , y = 3sin t

Answer 3

what relationship between sin t and cos t exists

Answer 4

to sole t is write instead of theta ?

Answer 5

if you square and add both the equations, you will eliminate theta

Answer 6

x^2 = 9 cos t^2 , y = 9 sin t^ 2 ???

Answer 7

its y^2 = 9 sin t^2
and yes, now add them, what u get ?

Answer 8

x^2 = 9 cos t^2 , y^2 = 9 sin t^2

Answer 9

solve them together or spread

Answer 10

i don"t speak eng good :(

Answer 11

don't forget to put brackets
x^2 = 9 (cos t)^2 , y^2 = 9 (sin t)^2
when you add them, u get
x^2+y^2 = 9[sin^2 t + cos^2 t]

u know what [sin^2 t + cos^2 t] equals ?

Answer 12

i don"t sure

Answer 13

[sin^2 t + cos^2 t] equals 1
so, finally u get
x^2+y^2 = 9

Answer 14

Thank you you're a genius Hahahah

Answer 15

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Answer 16

Thank you :)