Q. diketahui cosx=43, maka nilai dari sin2x adalah
Use Half-Angle Identity: We know that cos(x)=43. To find sin(2x), we can use the half-angle identity for sine, which is sin(2x)=±(21−cos(x)). We need to determine the sign (positive or negative) based on the quadrant in which x lies. However, since we are not given the quadrant, we will assume x is in a quadrant where sine is positive.
Plug in cos(x): First, we plug the value of cos(x) into the half-angle identity for sine: sin(2x)=±(21−cos(x))=±(21−43).
Simplify Expression: Now, we simplify the expression inside the square root: (1−43)=41. So, sin(2x)=±(41/2).
Take Square Root: Next, we simplify the fraction inside the square root: (41)/2=81. Therefore, sin(2x)=±81.
Rationalize Denominator: We take the square root of 81: 81=81=81. To rationalize the denominator, we multiply the numerator and the denominator by 8: 81×88=88.
Simplify 8: We simplify 8 to 22, because 8=4⋅2=4⋅2=22. So, sin(2x)=±(822).
Final Simplification: Finally, we simplify the fraction 822 by dividing both the numerator and the denominator by 2: sin(2x)=±(42).