Answer:
t = 8/5
Step-by-step explanation:
I'm assuming the equation given is the velocity of the particle
Derive the equation

Set it equal to 0 & solve for t

If you represent the problem in a diagram, you will form a triangle with 3 known length of the sides. When you are given all sides, and you are asked to find an angle, you can use the cosine law.
b^2 = a^2 + c^2 - 2ac*cosB
1.4^2 = 1.9^2 + 1^2 - 2(1.9*1)(cosB)
B = 45.78°
The answer is 3x- I just took the text