Answer: Option d.
Step-by-step explanation:
The trigonometric identity needed is:

Knowing that
:
Substitute it into
:

Simplify the expression:

Solve for
. Apply square root at both sides of the expression:


Answer:
-18root7
Step-by-step explanation:
-3root 84*3
-3root4*7*3*3
-3(2*3)root7
-18root7
Answer:
infinite solutions
Step-by-step explanation:
3x+15=3(x+5)
distribute
3x+15=3x+15
infinite solutions