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Spaceship approaching Mars and relative motion

Homework Statement
The spaceship S approaches Mars following the trajectory ##b-b## with velocity ##\vec v_S=19.3 \frac{km}{s}## with respect to the Sun. If Mars has a velocity ##\vec v_M=24.1 \frac{km}{s}## along the trajectory ##a-a## with respect to the Sun, determine the angle between ##SM## and ##b-b## such that a person inside the spaceship "sees" that Mars is moving towards him.
Homework Equations
##\vec v_{B/A}=\vec v_B - \vec v_A##
As the problem asks for the spaceship's perspective, I know that I should take ##\vec v_S=0## and ##\vec v_M=24.1-19.3## because the motion is relative to the spaceship. Then, the relative velocity of Mars and ##SM## should have the same direction. If they have the same direction, that angle would be 90°, wouldn't it? I mean, probably I'm forgetting something, but that's the way I tried to do it

20190906_202027777.jpg
 

RPinPA

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I know that I should take ##\vec v_S=0## and ##\mathbf{\vec v_M=24.1-19.3}## because the motion is relative to the spaceship.
The equation for ##\vec v_M## is a vector equation. So on the right hand side should be a vector subtraction. You have treated them as scalars.
 

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