Question

Question 2.

If 0 is an angle in the first quadrant, and cos(θ) = 0.669, determine the value of
cos(π - θ), cos(π + θ), and cos(4π - θ) using Symmetry.

Answer 1

1) -0.669

2) -0.669

3) 0.669

Explanation:

Since we are subtracting or adding multipled of pi, we will either obtain 0.669 or -0.669 as our answer for each of the three different questions.

Cosine is the x-coordinate in our orderes pairs. If our point ends up on the right side of the y-axis, the cosine will be positive. If our point ends up on left side, it will be negative.

Choose a thetha (I'm going to choose it in degrees) in the first quadrant to help with a visual.

If theta=70:

1) then 180-70=110 which is in second quadrant, so our cosines will be opposite in value.

2) then 180+70=250 which is in third quadrant, so our cosines will be opposite in value.

3) then 4×180-70=720-70=650 =1(360)+290 which ends up in the 4th quadrant which means the consines will have the same value.