Answer:
v = √ (v₁² - vₓ²)
θ = sin⁻¹ (vₓ / v₁)
Step-by-step explanation:
This is a speed composition exercise in kinematics, in the adjoint we can see the swimmer with speed v₁ and the river with speed vₓ, the resulting speed is v
To find these values we can use the Pythagorean theorem
v₁² = v² + vₓ²
v = √ (v₁² - vₓ²)
the direction the swimmer should take is
sin θ = vₓ / v₁
θ = sin⁻¹ (vₓ / v₁)