If A = B = 45°, then let us justify

sin (A+B) = sin A cos B + cos A sin B

If x² = sin² 30° + 4 cot² 45° - sec² 60°, then let us determine the value of x.

If x tan 30° + y cot 60° = 0 and 2x – y tan 45° = 1, then let us write, by calculating the values of x and y.

If A = B = 45°, then let us justify

cos (A+B) = cos A cos B – sin A sin B

In an equilateral triangle ABC, BD is a median. Let us prove that, ∠ ABD = cot ∠BAD