In this question, we use law of cosine which is

Substituting the given values of RS,RT, ST , we will get


Taking inverse cosine on both sides


Answer:
1 + x = 3
Step-by-step explanation:
x is 2
.............
Answer: -5/14
Step-by-step explanation:
I did the work and I rechecked the answer.
The answer is 1/r to the power of 9