Question

work out A=cos^-1(.875)

Answer 1

\[A=\arccos(0.875)\]
Really, there is no way to work it out other than using a calculator (I believe).

Answer 2

ok

Answer 3

By the way, \[0.875=\cos(A)\]
Although- watch out! Look at the second picture- the line x=0.875 intersects with the arcos graph infinitely many times, so A could be ANY of those values. Of course, teachers won;t expect you to find all the infinity of them, so you are normally given bounds to find A (within which there are 4 or so answers- remember than the cosine/arccos graph goes into the negative, too!)