Question

Is my answer correct?

Q: evaluate cos(15).

Answer:

Cos(45-30) = cos(45)cos(30) + sin(45)sin(30)
=(1/Sq root of 2)(Sq Root of 3/2)+(1/Sq root of 2)(1/2)
= (1+sq root of 3/2 sq root of 2)+(1/2 sq root of 2)
=sq root of 6+ Sq root of 2/4

Answer 1

first line is right, then i am confused

Answer 2

oh no first line is not right, should be plus not minus

Answer 3

\[Cos(45-30) = cos(45)cos(30) +sin(45)sin(30)\]

Answer 4

\[\frac{\sqrt{2}}{2}\times \frac{\sqrt{3}}{2}+\frac{\sqrt{2}}{2}\times \frac{1}{2}\]