Trig questions A level

[wide vigil]

I need help understanding something on 8b

I dont know why I cant use t as 7.2 to get the earliest time, idk why it has to be t=10.8

[golden sierra]

ok

[wanton wren]

Depth has to be at least 3.8

[wide vigil]

it says correct sin value should be 323.1 but i dont know why I cant use 216.9

[wide vigil]

t is time not depth tho and t can be in the interval 0 to 24

[golden sierra]

it arrives at 6:30 and stays for 2hrs

so the first time it can leave is 8:30

aka, t>=8.5

[wide vigil]

ohhh I didnt even read the question properly

[wide vigil]

thanbks

[wanton wren]

But you have to use D=3.8 and find t from that equation

[wide vigil]

thanks*

[golden sierra]

np

[golden sierra]

they got a valid t value

to solve the equation

its just the question has a detail that excludes that