Question

R=7/8cosθ+2sinθ

Which of the following gives the Cartesian form of the equation above?
Select the correct answer below:


x2+y2=7/10
y=−1/4x+7/8
y=−4x+7/2
8x2+2y2=7

Answer 1

Answer:y=−4x+7/2

Explanation:

Multiply each side of the equation by 8cosθ+2sinθ to get 8rcosθ+2rsinθ=7. Using the relationships x=rcosθ and y=rsinθ, the equation becomes 8x+2y=7. Solving this equation for y shows that y=−4x+7/2.

Answer 2

Answer: 8x^2 + 2y^2 = 7

Explanation:

The equation R = 7/8cosθ + 2sinθ can be rewritten in terms of x and y using the conversions x = Rcosθ and y = Rsinθ.

Substituting R = 7/8cosθ + 2sinθ into these equations, we get:

x = (7/8)cosθ cosθ + 2sinθ cosθ

y = (7/8)cosθ sinθ + 2sinθ sinθ

Simplifying these expressions using trigonometric identities, we get:

x = (7/8)cos^2θ + (4/8)sin2θ

y = (7/8)sinθ cosθ + (4/8)sin2θ

Multiplying both sides of the x equation by 8/7 and simplifying, we obtain:

8x^2 + 2y^2 = 7cos^2θ + 8sin^2θ

Using the identity cos^2θ + sin^2θ = 1, we get:

8x^2 + 2y^2 = 7(1)

Therefore, the Cartesian form of the equation is 8x^2 + 2y^2 = 7.