If we know that the vertex of angle a coincides with the origin, the starting edge coincides with the positive half axis of X axis, and the ending edge is on the line y = 3x, ask cos2a =?

If we know that the vertex of angle a coincides with the origin, the starting edge coincides with the positive half axis of X axis, and the ending edge is on the line y = 3x, ask cos2a =?

Given that the vertex of angle θ coincides with the origin, the starting edge coincides with the positive half axis of X axis, and the ending edge is on the line y = 2x, then Cos2 θ = ()
A. -45B. -35C. 35D. 45

According to the meaning of the question: Tan θ = 2, so Cos2 θ = 1sec2 θ = 1tan2 θ + 1 = 15, then Cos2 θ = 2cos2 θ - 1 = 2 × 15-1 = - 35

Given that the vertex of angle θ coincides with the origin, the starting edge coincides with the positive half axis of X axis, and the ending edge is on the line y = 2x, then Cos2 θ = ()
A. -45B. -35C. 35D. 45

According to the meaning of the question: Tan θ = 2, so Cos2 θ = 1sec2 θ = 1tan2 θ + 1 = 15, then Cos2 θ = 2cos2 θ - 1 = 2 × 15-1 = - 35

Given that the vertex of angle α is at the origin, the starting edge is on the positive half axis of X axis, the ending edge is on the line L: 2x-y = 0, and cos α < 0, point P (a, b) is a point on the end edge of α, and | op | = 5, the value of a + B is obtained

∵ the vertex of angle α is at the origin, the starting edge is on the positive half axis of X axis, and the ending edge is on the straight line L: 2x-y = 0, and cos α < 0, P (a, b) is in the third quadrant, a < 0, B < 0; ∵ Tan α = 2, namely Ba = 2, and | op | = 5, namely A2 + B2 = 5. The solution is a = - 1, B = - 2, ∵ a + B = - 3. The value of a + B is - 3