Answer :
Answer:
bro listen I don t know
Step-by-step explanation:
because I am in class7 this math problem is in class 9 or 10 th because my sister is currently in class 12 and she is rajasthan topper in 10 by achieving 98.95 % in class 10 th bro
Answer:
To prove this, let's start with the given equation:
sinA = 1/2 (b + 1/b)
We can rewrite sinA in terms of cosA using the Pythagorean identity:
sin^2 A + cos^2 A = 1
cos^2 A = 1 - sin^2 A
Now, square the given equation:
sin^2 A = (1/2)^2 (b + 1/b)^2
Expanding the right side:
sin^2 A = 1/4 (b^2 + 2 + 1/b^2)
Now, substitute cos^2 A:
1 - sin^2 A = 1 - 1/4 (b^2 + 2 + 1/b^2)
cos^2 A = 1 - 1/4 (b^2 + 2 + 1/b^2)
cos^2 A = 3/4 - 1/4 (b^2 + 1/b^2)
Now, recall that cos(2A) can be expressed as:
cos(2A) = cos^2 A - sin^2 A
Substitute the values we have:
cos(2A) = (3/4 - 1/4 (b^2 + 1/b^2)) - (1/4 (b^2 + 2 + 1/b^2))
Simplify:
cos(2A) = 3/4 - 1/4 (b^2 + 1/b^2) - 1/4 (b^2 + 2 + 1/b^2)
cos(2A) = 3/4 - 1/2 (b^2 + 1/b^2)
Thus, we've proven that cos(2A) = -1/2 (b^2 + 1/b^2).