Question

evaluate cos48cos42-sin48sin42

Answer 1

Answer:

0

Step-by-step explanation:

Cos48Cos42 - Sin48Sin42

= Cos(48 + 42)  ( ∵ CosACosB - SinASinB = Cos(A+B))

= Cos90°

= 0

Answer 2

The value of $\cos48^{\circ}\cos42^{\circ}-\sin48^{\circ}\sin42^{\circ}$ is 0.

Explanation:

We know that :

cos A= sin(90°- A)                  (1)

sin A = cos (90°- A)             (2)

The given expression : $\cos48^{\circ}\cos42^{\circ}-\sin48^{\circ}\sin42^{\circ}$

By using (1) and (2) , This will become:

$\cos48^{\circ}\sin(90^{\circ}-42^{\circ})-\sin48^{\circ}\cos (90^{\circ}-48^{\circ})$

$=\cos48^{\circ}\sin48^{\circ}-\sin48^{\circ}\cos48^{\circ}$

$=0$

Hence, the value of the given expression is 0.

# Learn more :

Cos²10+Cos²20+Cos²30+Cos²40+Cos²50+Cos²60+Cos²70+Cos²80+Cos²90.

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