Prove that cos 2theta - cos 4theta + cos 6theta - cos 12theta = 4 sin 3theta sin 5theta cos 4theta
2 answers:
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Answer:
0.1 or 1/10
Step-by-step explanation:
The digits 4, 5, 6, 7 and 8 are randomly arranged to form a three digit number, where the digits are not repeated.
This is question of permutation.
Imagine this sum as; there are 3 boxes(blank spaces for digits) and 5 different fruits(digits) are to be put in these boxes, where a box can hold a maximum of only 1 fruit. The number of such permutations are: ⁵P₃
By formula (a! is factorial a):
ᵃPₙ
⁵P₃
⁵P₃
⁵P₃
⁵P₃= 60
This is the total count of possible numbers that can be formed.
Now, for a number to be greater than 800 and even; first digit should necessarily be 8. Last digit can be 4 or 6. Using these conditions, there are 6 possibilities. 854, 864, 874, 846, 856, 876 are the numbers.
The probability that number is even and greater than 800 is: