Fermi
·
Concept Library
·
Courses
·
Books
·
Problems
·
Simulations
·
Math Wiki
·
High School
Fermi
›
Problems
Mathematics
Mathematics
Problem
Prove the following: 6.
cos
(
π
4
−
x
)
cos
(
π
4
−
y
)
−
sin
(
π
4
−
x
)
sin
(
π
4
−
y
)
=
sin
(
x
+
y
)
\quad \cos \left(\frac{\pi}{4}-x\right) \cos \left(\frac{\pi}{4}-y\right)-\sin \left(\frac{\pi}{4}-x\right) \sin \left(\frac{\pi}{4}-y\right)=\sin (x+y)
cos
(
4
π
−
x
)
cos
(
4
π
−
y
)
−
sin
(
4
π
−
x
)
sin
(
4
π
−
y
)
=
sin
(
x
+
y
)
Browse the problem library