Answer:
see explanation
Step-by-step explanation:
Using the sum/ difference → product formula
cos x - cos y = - 2sin( )sin (
)
sin x - sin y = 2cos ( )sin (
)
Given
(cosA - cosB)² + (sinA - sinB )²
= [ - 2sin()sin(
) ]² + [ 2cos(
)sin(
) ]²
= 4sin² ( )sin² (
) + 4cos² (
)sin² (
)
= 4sin² ( )[ sin² (
) + cos² (
) ← sin²x + cos²x = 1
= 4sin² ( ) × 1
= 4sin² ( ) = right side ⇒ proven
Answer:
is an even function.
Step-by-step explanation:
Recall when it means when a function is even or odd. An even function has the following property:
And an odd function has the following property:
So, let's test some values for cos(x).
Let's use π/3:
From the unit circle, was can see that this is 1/2 (refer to the x-coordinate).
Now, let's find -π/3. This is the same as 5π/3. Thus:
And again from the unit circle, we can see that this is 1/2.
Therefore, despite the negative, the function outputs the same value.
Cosine is an even function.
Notes:
Cosine is an even function and sine is an odd function. It's helpful to remember these as they can help you solve some trig problems!
