To measure the Eiffel Tower in Paris,

a person stands away from the base and measures the angle of elevation to the top of the tower to be 60◦. Moving 210 feet closer, the angle of elevation to the top of the tower is 70◦. How tall is the Eiffel Tower?

why is it wrong to do cos(60) = (210/x) getting x = 420

& then doing cos(20) = (x/420) getting that the Eiffel tower = 395 ft. ???

Any help would be really appreciated! thank you.