search
arrow-left Previous
Next arrow-right
Q: If f(x) = cos hx + sin hx, then which one of the following is correct?/ यदि f(x) = cos hx + sin hx , तो निम्नलिखित में से कौन सा एक सही है?
  • A. f(x) f(y) = f(x)+f(y)
  • B. f(x) f(y) = f(xy)
  • C. f(x) f(y) = f(x+y)
  • D.
    option image
Correct Answer: Option C - f(x) = cos hx + sin hx f(y) = cos hy + sin hy f(x) f(y) = (cos hx +sin hx) (cos hy +sin hy) =cos hx cos hy+sin hx cos hy+coshx sinhy+sinhx sinhy = cos h ( x+y) + sin h (x+y) = f(x+y) f(x) f(y) = f(x+y)
C. f(x) = cos hx + sin hx f(y) = cos hy + sin hy f(x) f(y) = (cos hx +sin hx) (cos hy +sin hy) =cos hx cos hy+sin hx cos hy+coshx sinhy+sinhx sinhy = cos h ( x+y) + sin h (x+y) = f(x+y) f(x) f(y) = f(x+y)

Explanations:

f(x) = cos hx + sin hx f(y) = cos hy + sin hy f(x) f(y) = (cos hx +sin hx) (cos hy +sin hy) =cos hx cos hy+sin hx cos hy+coshx sinhy+sinhx sinhy = cos h ( x+y) + sin h (x+y) = f(x+y) f(x) f(y) = f(x+y)