Khan Academy
Khan Academy: Find Trig Values Using Angle Addition Identities
Find the trigonometric values of various angles that (while they are not special angles) can be expressed as the sum or difference of special angles. Students receive immediate feedback and have the opportunity to try questions...
Khan Academy
Khan Academy: Using the Trig Angle Addition Identities
Find the trig values of sums of angles whose individual trig values are known. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.