Question
What is the value of cos(x + y) - sin(x - y) +
tan(2z)?Solution
cos(x+y) = cosx·cosy − sinx·siny sin(x−y) = sinx·cosy − cosx·siny cos(x+y) − sin(x−y) = cosx·cosy − sinx·siny − sinx·cosy + cosx·siny tan(2z) = 2·tanz/(1 − tan²z) So the whole value is cosx·cosy − sinx·siny − sinx·cosy + cosx·siny + 2·tanz/(1 − tan²z) Hence, Option 2 is corect
 = ? If (a + b) = 1 and (1/a) – 2b = 5/a then find the value of a2 + b2.
If √t + (1/√t) = 5, then find the value of t + (1/t).
Solve for x:- 5(x − 2)/3 = 3(x + 4)/2
when x =4 and y =-6 then find the value of 27x³ +58x²y +31xy² +8y³?
If √b + (1/√b) = 8, then find the value of b + (1/b).
(408 × 680)÷(20% of 680) = (250 × 260)÷ 10 + ? – 4500
If x : y : z = 6 : 7 : 11, and (2x + 3z) = 180, then find the value of y.
  = ?If (x + y) = 35, then find the value of (x - 10)6 + (y - 25)6.
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