Question

Prove it . cos (x+y) cos (x-y)

Answer 1

Step-by-step explanation:

Solution :

cos(x + y) cos(x – y)

➡ (cos x cos y – sin x sin y)(cos x cos y + sin x sin y)

➡ cos²x cos²y – sin²x sin²y

➡ cos²x(1 – sin²y) – (1 – cos²x) sin²y

➡ cos²x – cos²x sin²y – sin²y + cos²x sin²y

➡ cos²x – sin²y.

Hence :

Proved.

Answer 2

Step-by-step explanation:

Find the height of a cylinder whose radius is 7 cm and the total surface area is 968 cm2.