# math help

posted by .

I really don't understand how to write the expression as one invloving only sinϴ and cosϴ

sin2ϴ+cos3ϴ

• math help -

first of all you should by now have proven that
sin 2x = 2sinxcosx

by writing cos 3x as cos(2x + x), expanding that and then changing the cos 2x and sin 2x factors you can show that
cos 3x = cos^ 3x - 3 sin^2 x cos x

## Similar Questions

1. ### cHEM II

Consider a titration of 50.00 mL of 0.1005 M HCl with 0.1012 M NaOH.
2. ### math 1012

what is the sum of the lengths 39cm and 2m
3. ### Math

Hexadecimals, binary numbers. It's not regular addition and multiplication. G. 11112 + 10102 = H. 1012 x 100012 =
4. ### Math

5. Suppose that the volumes of four stars in the Milky Way are 2.7 × 1018 km3, 6.9 × 1012 km3, 2.2 × 1012 km3, and 4.9 × 1021 km3. What is the order of the stars from least to greatest volume?
5. ### differetial calculus-related rates

LINEAR VS ANGULAR SPEED A wheel of a radius 30 centimeters revolves at a rate of 10 revolutions per second.A dot is painted at a point P on the rim of the wheel. a)find dx/dt as a function of ϴ. b)use a graphing utility to graph …
6. ### Math

Solve each problem and write your answers in scientific notation. 1. (6.0 x 105) x (3.0 x 104) = (1 point) 18 x 1020 18 x 109 1.8 x 1020 1.8 x 1010 2. (5 x 10–2) ÷ (2 x 103) = (1 point) 2.5 x 10-5 2.5 x 10-1 25 x 101 25 x 102 3. …
7. ### Intro to Ecology

Global estimates of denitrification in terrestrial ecosystems vary widely but are of the order 200*102 g/yr, and more than half of that total occurs in wetland ecosystems. If restoration results in an increase in wetland area by approximately …
8. ### Trigonometry

Find (sinϴ + cosϴ) if the terminal side of ϴ passes through (5,2)
9. ### math

Solve each problem and write your answers in scientific notation. 1. (6.0 x 105) x (3.0 x 104) = (1 point) 18 x 1020 18 x 109 1.8 x 1020 1.8 x 1010 2. (5 x 10–2) ÷ (2 x 103) = (1 point) 2.5 x 10-5 2.5 x 10-1 25 x 101 25 x 102 3. …