Do Question no 4 in picture pls If cos theta 35 and 90 degr

Do Question no 4 in picture pls

If cos theta = -3/5 and -90 degree lessthan theta lessthan 0 degree, then find tan theta/2. Use half-angle formulas to find the exact value of sin 15 degree. Semicircle Squareroot 1 - Squareroot 3/2 Semicircle Squareroot 1 + Squareroot 3/2 Semicircle Squareroot 2- Squareroot 3/2 Semicircle Squareroot 2 + Squareroot 3/2

Solution

sin15

Use the formula : cos2x = 1 -2sin^2x

sinx = sqrt{[ 1 -cos2x]/2}

sin15 = sqrt{[1-cos30]/2}

= sqrt(2 - sqrt(3))/2

Option 3