Addition: 70 + 80 = 150. You round 65 up because the ones digit is greater than and the same with 77.
Multiplication: Round up since both ones digits are bigger than 5. 70 x 80= 5600.
In (A), we have 9 : 2.
Multiply by 2, we get 18 : 4
In (B), we have 36 : 8.
Divide by 2, we get, 18 : 4.
In (D), we have 54 : 12.
Divide by 3, we get, 18 : 4.
Hence, (C) is not equivalent to the given statement.
<u>Answer and explanation</u>
(1+sinθ)(1-sinθ)=cos²θ
We are to prove that the left hand side is equal to the right hand side.
(1+sinθ)(1-sinθ) = 1(1-sinθ) + sinθ(1-sinθ)
= 1 - sinθ + sinθ - sin²θ
= 1 - sin²θ
From the trigonometric identity sin²θ + cos²θ = 1,
1 - sin²θ = cos²θ
