Answer:
y = 6.22
You can solve this in two ways.
1.) Use SOH CAH TOA:
I typically start off by labeling the sides of the triangle with H (hypotenuse), O (opposite), and A (adjacent). Because I need to figure out what y is when given an angle and 4, I will use CAH, or cosine.
![\cos(angle) = (adjacent)/(hypotenuse)](https://img.qammunity.org/2021/formulas/mathematics/high-school/vj66pnfbonbxtq6u7jmm821vezmka02k9g.png)
![\cos(50) = (4)/(y)](https://img.qammunity.org/2021/formulas/mathematics/high-school/4w4f35f5r75b7rxdraiexsgt7cqmdwgy7o.png)
![\cos(50) * y = 4](https://img.qammunity.org/2021/formulas/mathematics/high-school/6gwcchzujnya2uqp4kf6tr3lk11zizoj9l.png)
![y = (4)/( \cos(50) )](https://img.qammunity.org/2021/formulas/mathematics/high-school/a52uek8ulm57fy0ntyg15rseuk5io66m1t.png)
![y = 6.22](https://img.qammunity.org/2021/formulas/mathematics/high-school/dyp2cb8nkrkoylvindb9c7o9urwke9d6i9.png)
2.) Use Law of Sines:
Solve for the last angle inside the triangle first.
![180 - (50 + 90) = 40](https://img.qammunity.org/2021/formulas/mathematics/high-school/rxawv2k2fzoatc2cvhd6c932tf11112pmy.png)
Then use the angle you found (40°) in the equation.
![(4)/( \sin(40) ) = (y)/( \sin(90) )](https://img.qammunity.org/2021/formulas/mathematics/high-school/cul98o4iiidak29zziio1rlxmd7ls3jtzr.png)
![(4)/( \sin(40) ) * \sin(90) = y](https://img.qammunity.org/2021/formulas/mathematics/high-school/cfdfbe3wofi7z6grydpk3oeofdymz9qn1k.png)
![y = 6.22](https://img.qammunity.org/2021/formulas/mathematics/high-school/dyp2cb8nkrkoylvindb9c7o9urwke9d6i9.png)