Hi All,
I am brushing up on AS Level maths and cannot agree with a text book answer.
Question.
Find the least positive value of the angle x.
sin (5x + y) = cos ( y – 3x)
Answer : I use sin z = cos ( 90  z ) so z = 5x + y and 90  z = y  3x.
Simplifying 5x + y = 90  y + 3x infers x + y = 45.
I deduce x is the smallest positive value.
The book's answer is 11.25.
Many thanks for your time.
Nigel.
