Answer:
B.
Step-by-step explanation:
8÷2=4
12÷3=4
20÷5=4
28÷7=4
t⋅(14−5)
distribute
14t -5t
Choice A
7a
The value of cos Ф is ±
There are important rules for sin Ф and cos Ф
∵ sin Ф =
∴ sin²Ф =
→ By using the third rule above
∵ cos²Ф = 1 - sin²Ф
∴ cos²Ф = 1 -
∴ cos²Ф =
→ Take square root for both sides
∴ cos Ф = ±
∴ The value of cos Ф is ±